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LIBRARY OF CONGRESS. 

Chap._„k__ Copyright No. 

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UNITED STATES OF AMERICA. 



ELEMENTS 



OF 



PHYSIOLOGY 



AND 



HYGIENE. 



BY 



R. T. BROWN, M.D., 

PROF. OF PHYSIOLOGY, MED. DEPT., INDIANA E v " r ERSITY. 



NEW-YORK •:• CINCINNATI :• CHICAGO 
AMERICAN BOOK COMPANY 



TWO COPIESR£o£iV^ 

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55821 



Entered according to Act of Congress, in the year 1 872, by 

WILSON, H1NKLE & CO., 

In the Office of the Librarian of Congress, at Washington, D. C. 

Copyright, 1900, by Nancy T. Brown. 

BROWN DUYS & HY. 



SECOND OOi J 'Ki 






PREFACE. 



The following lessons in Physiology and Hygiene were prepared 
in response to a resolution of the Indiana State Teachers' Asso- 
ciation. They were designed originally to meet a demand in that 
State, where the law introduces these branches of study into common 
schools. In the execution of this design the author has endeavored to 
prepare a work adapted to the wants of families and the general 
reader. 

Physiology and Hygiene having been but recently introduced into 
the common literature of the country, parents, generally, have only a 
limited knowledge of a subject which stands in most intimate connec- 
tion with the well-being of those intrusted to their care. To such 
persons the following lessons present the elementary principles of 
human physiology, and the laws of health, deduced therefrom, di- 
vested, as far as possible, of the technical dress which too often 
places these subjects beyond the comprehension of common readers. 

It is of the first importance to those who have the care of chil- 
dren, whether in the family or the school, that they make themselves 
familiar with the laws of health, in order that they may establish, in 
early years, habits of correct living in those under their charge. The 
value and duration of human life are more intimately connected with 
the establishment of such habits than is generally admitted. If wrong 
ones are formed in childhood, the power to correct them in maturer 
years is often wanting ; and even if efforts in that direction prove 
successful, still the evil consequences remain. 

It must be remembered that habits injurious to health, when estab- 
lished in youth, while the vital organs are in a state of development, 
leave an impression of a deeper and more permanent character than 
similar habits formed in after life. To prevent these evils rather than 
to reform them is the true philosophy. 

To this end the author invokes the aid of parents and teachers, and 
as his contribution to what he conceives to be the best method of 
instruction, presents these lessons, trusting they will tend toward 
awakening an interest in subjects of vital importance to all. 



iv PEEFACE. 

Many text-books on the science of Physiology and Hygiene "have 
been presented to the schools and colleges of this country during the 
past few years. These are chiefly abridgments of the larger works 
used in medical colleges ; and as physiology is taught in those schools 
with a direct reference to the cure of disease, these books retain more 
or less of this character. But the study of physiology in other than 
medical schools should have direct reference to the Reservation of health, 
rather than to the cure of disease. It has been the leading purpose of 
the author to make hygiene the prominent feature of this book, and 
all other studies introduced subordinate to it. 

To the scientific reader the author wishes to say, that while he has 
aimed to present his subject in a popular form, and avoid the discus- 
sion of many purely scientific questions which might have been intro- 
duced, it has, at the same time, been his purpose to treat it in the light 
of the latest discoveries. 

In the use of such terms as vital force, etc., the author does not 
intend to commit himself to any particular theory of life, but merely 
uses such phrases as signs of the unknown. 



HINTS TO TEACHERS. 



This book is divided into fifty lessons, with the intention of adapt- 
ing it to the common division of the school year into terms of about 
twelve weeks each. If five lessons are recited each week, the work can 
be completed in a term, and ten recitations be left for review. 

If it is desirable to give more time to the study, the lessons may 
be divided and the work distributed over two terms, devoting the first 
to Physiology and the second to Hygiene. 

For the purpose of easy reference, the work is divided into sections 
and each one is numbered. To adapt it to the method of teaching by 
topics, each section is introduced by a head-line in full-faced type, 
embracing the leading subject. 

Brief recapitulations are appended to the lessons, for. the assistance 
alike of teachers and pupils in the work of reviewing. 

Much of the work of teaching this science should be done by lec- 
tures, or by familiar conversations between pupils and the teacher; 
and in the arrangement of the matter of these pages this feature has 
been kept constantly in view. 



CONTENTS. 













Page 


Lesson I. — Introduction 7 


Lesson II. — Definitions and Classifications 








. 13 


Lesson III. — Nutrition .... 








. 19 


Lesson IV. — Digestion 










24 


Lesson V. — Circulation . 










31 


Lesson VI. — Circulation — Continued 










3G 


Lesson VII. — Respiration . 










41 


Lesson VIII. — Purification of the Blood 










. 46 


Lesson IX. — Growth and Kepair 










. 52 


Lesson X. — System of Voluntary Motion 










. 58 


Lesson XI. — Skeleton 










. G3 


Lesson XII. — Muscles 










. 72 


Lesson XIII. — Muscular Motion — Voice 










. 78 


Lesson XIV. — Nervous System . 










. S3 


Lesson XV. — Nervous System — Continued 










. 90 


Lesson XVI. — Sensation .... 










96 


Lesson XVII. — Organs of Special Sense 










101 


Lesson XVIII. — Hearing . 










106 


Lesson XIX.— The Eye 










. Ill 


Lesson XX. — Vision .... 










117 


Lesson XXI. — Vision — Continued 










. 123 


Lesson XXII. — Motor Functions 










128 


Lesson XXIII.— Nervous Functions . 










. 133 


Lesson XXIV.— Mental Functions 










138 



(v) 



VI 



CONTENTS. 



Lesson XXV. — Sleep . 

Lesson XXVI.— Health .... 

Lesson XXVII. — Food and Drink 

Lesson XXVIII. — Classification of Food . 

Lesson XXIX.— Quality of Food 

Lesson XXX. — Quality of Food — Continued 

Lesson XXXI. — Mode of Preparing Food 

Lesson XXXII. — Auxiliary Food 

Lesson XXXIII. — Quantity of Food . 

Lesson XXXIV.— Time of Taking Food 

Lesson XXXV. — Condition of the System 

Lesson XXXVI. — Circulation 

Lesson XXXVII.— Breathing . 

Lesson XXXVIII.— Pure Air . 

Lesson XXXIX. — Animal Heat 

Lesson XL. — Bathing — Clothing 

Lesson XLI. — Hygiene of Bones 

Lesson XLII. — Muscular Exercise 

Lesson XLII!. — Exercise and Eest 

Lesson XLIV. — Brain Best 

Lesson XLV. — Brain Poisons 

Lesson XLVI. — Brain Poisons — Continued 

Lesson XLVII. — Brain Poisons — Continued 

Lesson XLVI II. — Tobacco 

Lesson XLIX. — Brain Exercise and Best . 

Lesson L. — Accidents and Diseases . 



Page 

143 
149 
154 
160 
165 
170 
175 
180 
185 
190 
196 
201 
206 
211 
216 
222 
227 
232 
237 
242 
248 
253 
258 
263 
268 
273 



PART I. 

PHYSIOLOGY. 



LESSON I. 



INTRODUCTION. 



1. Classification of Bodies. — The material things 
that are around us in this world may be divided into 
two classes — those which were formed by the coming 
together of particles of matter under the simple laws 
of attraction, and those which have grown to their 
present size and shape under the influence of that force 
which we call Life. 

Chemistry teaches us how the first class of bodies is 
formed; and Mechanical Philosophy tells how they op- 
erate on each other, and defines the laws governing 
their movements. 

Physiology instructs us in the mysteries of life-formed 
bodies, as far as these may be known. It may therefore 
very properly be called The Science of Life. 

2. Organic Bodies. — The difference in the growth of 
a living body, and the increase in size of a body which 

(V) 



8 PHYSIOLOGY. 

is not alive, have given rise to the following method of 
classifying and naming bodies, which is now very gen- 
erally received. 

A plant takes up the matter intended for its growth 
by means of vessels, or open mouths provided for that 
purpose, either in its roots or leaves. In these vessels, 
this matter undergoes the changes that fit it to become 
a part of the living plant, and by them it is carried to 
its proper place and built into the structure of the body. 
These instruments by which the food is absorbed, pre- 
pared, and deposited are called Organs, and the body thus 
formed is an Organic body. 

3. Inorganic Bodies. — A stone placed in water which 
holds lime dissolved in it, as the waters of many springs 
do, will increase in size by the addition of particles of 
lime to its outer surface; but in making this apparent 
growth, no vessels are employed to carry the lime to its 
place, and no instruments are used to change either its 
form or place. 

A rock thus formed is, therefore, an Inorganic body. 
These two classes embrace all bodies of matter on the 
earth. To the inorganic group belongs the great mass 
of material of which the globe is formed, such as rocks, 
earths, metals, etc. 

4. Character of Organic Bodies. — The organic world 
is made up of but a few simple elements; but the bodies 
are very complex, both in their form and composition. 
They are, moreover, much less fixed and permanent in 
their character than inorganic bodies. 

While an organic body lives, it is constantly under- 
going change by growth, or by decay and repair; and as 
soon as it ceases to live, a tendency to decomposition 



INTRODUCTION. 9 

ensues, and the body — it may be slowly, but very 
surely — returns its matter to the inorganic world from 
which it was taken. 

5. Division of the Organic World.— Organic bodies 
are of two kinds — Vegetable and Animal. These are alike 
formed under the influence of the life-force, and by 
means of organs, yet they differ from each other in their 
general characteristics. This difference is most apparent 
in the higher and more perfect forms of both classes; 
but as we descend in the scale of life, these two grand 
divisions approach so near to each other that it is al- 
most impossible to define the line separating them. 

The distinction w T hich most persons would first ob- 
serve is that plants are fixed to one spot, w r hile animals 
enjoy the power of changing their place. While this is 
generally true, it is not so universally. The sponges 
and corals of the ocean are as firmly fixed to one spot 
as the trees of the forest. 

6. Animal Characteristics. — Animals are described 
as having a nutritive cavity — a stomach into which 
food is taken, and where it is prepared to be used for 
the growth and repair of the living body. In the veg- 
etable, the food is absorbed either by the roots or leaves, 
and it undergoes no previous preparation to fit it to be 
thus absorbed. 

This distinction applies only to those animals whose 
structure conforms to the regular types of animal life. 
No internal cavity can be found in many of the lower 
and irregular forms of animal life. Plants live on inor- 
ganic food; animals digest and assimilate only that 
which has been organized. This, in the strict meaning 
of its terms, is true; yet it is evident that animals ap- 



10 PHYSIOLOGY. 

propriate water, and various mineral substances, though 
probably without any digestive change. 

7. Nervous System — the true distinction.— The real 
difference between animal and vegetable life consists in 
the possession of a Nervous System, and the manifestation 
of its functions, in a greater or less degree, by all ani- 
mals. These are the powers of sensation, perception, 
and voluntary motion. In the lower forms of animal 
life, the nervous system is very imperfect; yet the un- 
mistakable evidence of feeling, and the power to move 
at the command of the will, though the motion may be 
to a very limited extent, demonstrate its existence, even 
though the microscope may not reveal the nervous cen- 
ters. 

8. Animal Sub-kingdoms. — While all animals have 
an apparatus of voluntary motion, and organs for receiv- 
ing, transmitting, and perceiving sensations, yet the 
degree of perfection in which these animal powers are 
possessed, is so widely different as to give room for the 
division of the animal kingdom into several sub-king- 
doms, each distinguished by some common element of 
form, which constitutes what is called the type of the 
sub-kingdom. 

At the base of the pyramid of animal life lies a group 
of forms, exceeding in numbers, perhaps, all other classes 
of animals, yet so minute as to be seldom visible to the 
naked eye, and are therefore studied chiefly by aid of 
the microscope. They are called Protozoans, a word 
which means first life. These are exceedingly simple, 
yet they present endless varieties of form. As they 
do not conform to any special type, they are very 
difficult of classification. 



INTRODUCTION. 



11 



Rising above these, we have four well defined types 
of life, which we enumerate in the ascending order. 



Fig. 1.— Stab-Fish. 




1st. Radiate Animals, or those with arms or feelers ex- 
tending in every direction, like rays, from the mouth, 
which is simply an opening into the central, digestive 
cavity. 



Fig. 2.— Snail. 




2d. Mollush, or soft-bodied animals without limbs; 
such as snails, oysters, clams, etc. 

Fig. 3-Dragon-Fly. 




3d. Articulates, or animals whose bodies are made of 



12 



PHYSIOLOGY. 



Fig. 4. 



rings joined together, as in the lobster, craw-fish, and in- 
sects generally. 

4th. Vertebrates. Animals with a bony col- 
umn extending the whole length of the body, 
and inclosing a nervous cord with a more or 
less perfectly developed brain at its forward 
termination. 

9. Classification of Vertebrate Animals.— 

Of this last and most perfect type of animal 
life we enumerate, in the ascending order, 
four grand sub-divisions, distinguished from 
each other by very well marked natural pecu- 
liarities. These are: 

1st. Fishes. Inhabiting the water, and 
breathing by means of gills. They are usu- 
ally covered with scales. 
2d. Reptiles. Breathing air with very imperfectly 
formed lungs, and general^ having the body naked. 
Fishes and reptiles are cold-blooded animals, the tem- 
perature of the body being nearly that of the water or 
air in which they live. 

3d. Birds. Warm-blooded animals, covered with feath- 
ers, and provided with wings for flying. With the ex- 
ception of a few reptiles, these three classes produce their 
young from eggs. 

4th. Mammals. Animals which suckle their young. 
Their bodies are usually covered with hair. 




Recapitulation. 

An Organ is any thing used as an instrument to accomplish a 
purpose. 

That which is done by an organ is called its function. Exam- 
ple : The teeth are organs ; chewing food is their function. 



DEFINITIONS AND CLASSIFICATIONS. 13 

A body which grows and maintains its repairs, by means of the 
life force exerted through organs, is called an Organic body, and 
the laws regulating the proper action of these organs constitute 
its Physiology. 



LESSON II. 

DEFINITIONS AND CLASSIFICATIONS. 

10. Range of Physiological Science. — Anatomy de- 
scribes the different parts or organs of an organic body, 
while Physiology teaches the use of each organ, and 
describes its mode of action. As we have vegetable and 
animal bodies, and both are organic, so we have vegeta- 
ble anatomy and physiology, and animal anatomy and 
physiology. The first of these belongs properly to the 
science of Botany ; the last is very appropriately divided 
into two sections : Comparative Anatomy and Physiol- 
ogy, and Human Anatomy and Physiology. 

The first of these sections is devoted to the peculiar 
forms of the several organs and their functions in the 
lower animals, as compared with the corresponding or- 
gans and functions in the human body. 

11. Limits of the present study.— In the following 
pages w^e propose to confine the discussion to the subject 
of Human Anatomy and Physiology, chiefly. No more 
of descriptive anatomy will be given than will enable 
the reader or student to understand the functions of the 
-everal organs described, and to treat these organs and 
functions so as to maintain, in the most perfect manner, 
then natural condition and proper action. This is 
health. 



14 PHYSIOLOGY. 

What Life is, we may not know; but what it does, 
and the laws by which it acts, are legitimate subjects 
of knowledge, as clearly within our reach as any other 
science. 

12. Animal and Vegetable Nutrition — the differ- 
ence, — Though the laws of animal life, in their leading 
and essential features, are the same in the lower ani- 
mals as in man, yet in many of the details, both in the 
form of special organs, and the manner in which these 
perform their functions, there is a wide difference be- 
tween the merely animal and the human. 

All living bodies grow by absorbing substances unlike 
that of their own body, and by so changing it as to 
convert it into a substance exactly like that of their 
own organs. This is nutrition, and is a function com- 
mon to all organic bodies. In vegetables, the matter 
thus appropriated remains a part of the body till the 
whole structure or organ dies, and by decay returns to 
the inorganic world. 

In animals the matter furnished by nutrition, after 
it has served its purpose for a time, is removed, particle 
by particle, new matter being prepared and furnished 
by digestion to supply the place of the worn-out par- 
ticles removed. 

13. Animal Functions. — The work of repair is a feat- 
ure which characterizes animal life, and is common to 
all its forms ; indeed, this change of matter is not only 
common to all animals, but is essential to the mainte- 
nance of active life in them. 

The manner in which motion is performed, is the 
same in man as in all other animals, however widely 
they may differ from the human form, or from each 



DEFINITIONS AND CLASSIFICATIONS. 15 

other. The breathing apparatus differs in many par- 
ticulars in different animals; but to breath air, either 
by itself or in mixture with water, is a condition of 
active life from which no animal can escape. 

U. Relation of Man to the lower Animals. — In all 

these respects man is an animal, but in other respects he 
is more than an animal. He has many characteristics 
that are purely human. In the frame-work of his body, 
man is constructed for an upright position; while in all 
other animals the natural position is that in which the 
spinal column, or backbone, is horizontal, or nearly so. 
Even the monkey when taught to stand erect does so 
with evident difficulty, and all his movements show his 
position to be a constrained one. 

The configuration of the human face differs in many 
features from that of any other animal. For example : 
the lower jaw of all the inferior animals drops back im- 
mediately from the front teeth, while that of man pro- 
jects fonvard, forming a chin. Certain very expressive 
functions or actions are peculiar to man, such as the 
power to shed tears, to laugh, to communicate his 
thoughts by articulate language, etc. 

15. Classification of Man. — Naturalists concur in 
placing man at the head of the animal creation. They 
place him in an order distinct and separate from all 
other animals; and recognizing the fact that he alone 
has two hands, they name that order Bimana; while 
monkeys are regarded as four-handed animals, and there- 
fore as constituting the order Quadrumana. 

If w T e study carefully the structure of that w r onderful 
organ — the human hand, and observe closely its marvel- 
ous endowments and capabilities, we shall hardly be 
B. P.— 2. 



16 PHYSIOLOGY. 

willing to say that a baboon is furnished with four such. 
organs! The feet of a monkey are not real hands. 

16 # Mental and Moral Distinctions. — But it is chiefly 
in the perfection of his nervous system, and his superior 
mental endowments, that man rises above the mere ani- 
mals that surround him, and stands alone in his endow- 
ments and capacities. The inferior animals certainly 
think and make inferences with regard to matters of 
their own personal experience — and so far they may be 
said to reason ; but they are wholly incapable of reason- 
ing on the abstract qualities of things, or of deducing 
general truths from special manifestations. 

The moral sense — the abstract idea of right and 
wrong — is exclusively a human faculty, and belongs to 
man's spiritual nature. This is not merely a higher 
degree of the reasoning power of brutes, but a different 
kind of reasoning. 

17. Abstract Thought — a human attribute, — It is 

to this power of abstract thought that man is indebted 
for his ability to contrive and construct machines to re- 
lieve his hands from the drudgery of manual toil; by 
this he discovers and applies natural laws, invents sci- 
ence, and perfects literature. While he is un animal — 
a very perfect animal in all his physical organs and 
faculties — he is something more than an animal in 
this. 

This superior mental endowment should be made the 
basis of his classification; and as only organic life is 
displayed in the vegetable world, and this, with the 
animal-powers of sensation and volition superadded, is 
embodied in the animal kingdom, so both these, with the 
powers of abstract reason, moral sensibility, and the 



DEFINITIONS AND CLASSIFICATIONS. 17 

devotional attributes of his nature mark him as belong- 
ing to a grade of Life as much above the mere animal 
as the animal is above the vegetable. 

18. Form of Matter composing the Organs of the 
Body. — But our present task is to study man in the 
structure of that body which he has in common with 
other living organisms, and in the laws by which the 
various movements of that complicated machine are 
governed. Before entering on the study of this subject 
in detail, a few general statements and explanations 
may be of use in its introduction. 

The human body is composed of solids, semi-solids, 
and fluids. These are constantly changing while the 
body lives. The semi-solid flesh, as well as the firm, 
compact bone, was once fluid in the form of blood ; and, 
in due time, particle by particle, they will be dissolved, 
and becoming fluid again, will be carried away. 

19. Tissues — their several offices. — The several 
parts of the body differ from each other in the character 
of their structure as well as in the substances out of 
which they are formed. These different structures are 
called Tissues. So we have the bony or osseous tissue in 
the bones which form the solid frame-work of the body; 
the fibrous tissue in the muscles which move these bones ; 
the membranous tissue in the delicate skin or membrane 
which covers each organ, and lines every cavity of the 
body; the areolar or cellular tissue which fills all the 
spaces between the organs, and gives roundness and 
symmetry to the outlines of the body; the nervous 
tissue, that delicate structure seen in the substance of 
the brain, and in those white cords — the nerves — which 
extend from it to all parts of the body. 



18 PHYSIOLOGY. 

20. The three Systems. — The living human body, 
though evidently a unit, may yet be regarded, in its 
varied and complicated actions, as three systems acting 
in concert with each other. These are : 

1st. The System of Nutrition, consisting of the apparatus 
of Digestion, of Circulation, and of Respiration. 

2d. The System of Voluntary Motion, consisting of a bony 
skeleton with its joints and ligaments, and a muscular 
apparatus so constructed and arranged as to produce a 
great variety of motions. 

3d. The System of Nervous Sensibility and Motor Force. 
This consists of the brain and spinal cord, with numer- 
ous nerves branching and ramifying through every tissue 
of the body. These several systems w^e shall proceed to 
consider in order. 

Recapitulation. 

Comparative Physiology likens the organs of inferior animals 
to those of man. This book treats of organs and their functions 
chiefly with reference to the preservation of health. 

Vegetables acquire matter for growth which becomes perma- 
nent. Worn-out animal matter is replaced by new. Man is 
more than an animal in figure, face, and functions. Man forms 
the order Bimana; is distinguished by mental capacity, moral 
nature, and capability for abstract thought. 

The body is composed of solids, semi-solids, and fluids. Tis- 
sues are osseous, fibrous, membranous, areolar, and nervous* 
The three systems in one body. 



NUTRITION. 19 



LESSON III. 

NUTRITION. 

21. Classification of Food.— The process of supplying 
material fitted for the growth and repair of the living 
body is properly nutrition; but as the maintenance of 
animal heat is intimately connected with this matter 
of nutrition, w r e shall consider them together, as parts 
of one process. 

The crude material of nutrition is known by the gen- 
eral name of Food. This consists, how r ever, of two classes 
of substances — that which supplies the material for the 
growth, and also to repair the wastes of the several 
tissues of the body; and that which, being consumed, 
constantly gives off heat to maintain the uniform tem- 
perature of the body. 

The first class, from the close resemblance, in chem- 
ical composition, which all the articles of it bear to al- 
bumen (which is the substance of the white of eggs), is 
called albuminate food, and the latter class is known 
as carbonaceous food. 

22. The Month — its functions. — The first act of nu- 
trition is performed in the mouth, and is called mastica- 
tion. It consists of crushing and grinding the food, thus 
reducing it to a state of fine division, and at the same 
time moistening it w r ith a fluid furnished for the pur- 
pose called saliva. The mouth, where this work is done, 
is lined with a smooth covering alw r ays kept moist, when 
in a healthy condition, by a glairy fluid known as 
mucus, and hence this surface is named the mucous 
membrane. 



20 



PHYSIOLOGY. 



This kind of a membrane lines all cavities of the body 
which communicate in any way with the air; while all 
the closed cavities, and the organs contained in them, 
are lined and covered with a dense, smooth, shining 
coat, called a serous membrane. 



Fig. 5-Peemaxent Teeth. 






a. Incisors. b. Cuspids. c. Bi-cuspids. d. Molars. e. Wisdom-teeth. 

23. Mastication— Classification of the Teeth.— The 
grinding of the food is performed by the Teeth. These 
are composed of a very hard, compact, bony substance, 
covered with a material still harder called enamel. 
There are two sets of teeth. The first, or temporary 
teeth, consists of ten in each jaw. They appear in in- 
fancy, and continue six or eight years, when they become 
loose and are crowded out by the permanent teeth. Of 
these there are sixteen in each jaw, or thirty-two in all. 

The teeth are divided into four classes, as follows: 
The four front teeth in each jaw are called incisors, or 
cutting-teeth; the next tooth on each side of these is 
the cuspid, or canine-tooth; next follow two bi-cuspids 



NUTRITION. 



21 



on each side; and. Lastly, three molars, or grinding- 
teeth, in each jaw. The last of these, on each side, is 

called the wisdom-tooth, because it does not appear 
until a person is twenty, and sometimes twenty-live 
years old. 

Fig. 6.— Salivary Glands. 




a. Parotid gland. b. Parotid duct. c. Sublingual gland. 
d. Submaxillary gland. e. Submaxillary duct. 



24. Salivary Glands.— The saliva, with which the 

food is moistened in mastication, is furnished by a set 
of bodies called Salivary glands, whose office it is to 
separate this fluid from the blood. All the special fluids 
of the body are produced in a similar manner, so that 
the glands form an important group in the vital econ- 
omy. Their action is called secretion. 

The salivary glands are three in number on each 
side. The largest of these, called the Parotid gland, is 



22 PHYSIOLOGY. 

situated behind the angle of the lower jaw, and forward 
of the external ear. It sends its saliva into the mouth 
through a tube or duct which opens opposite the second 
molar tooth, in the upper jaw. 

The second pair, the Submaxillary glands, are located 
on the inner side of the lower jaw, a little forward of 
the angle, on each side. The Sublingual glands are 
placed beneath the mucous membrane, forming the 
floor of the mouth, on each side, near the base of the 
tongue. 

25. Saliva — its use, — The movement of the jaw in 
the act of chewing excites these glands to activity, and 
they pour out a bland fluid, nearly transparent and a 
little heavier than water. This saliva, when mixed with 
food of the. nature of starch, has the power of slowly con- 
verting it into sugar. Now starch, which forms the 
greater part of bread, potatoes, and such articles of food, 
will not dissolve in water; but when converted into 
sugar, it is very readily dissolved. It will be observed, 
then, that the saliva is not intended merely to moisten 
the food that it may be swallowed easily. Tea, cofree, 
water, or milk may be used for that purpose, but neither 
of these can be substituted for saliva without injuring 
digestion, for neither of them can change starch into 
sugar, or render it soluble in water. 

26. Pharynx — its office. — In the act of chewing, the 
tongue is used to keep the food pressed between the 
teeth; and finally, when it is thoroughly reduced to a 
pulp, the tongue rolls it into a little ball, and carries it 
along its upper surface to the back part of the mouth, 
passes it between the pillars of the fauces, and under the 
hanging palate. These organs form a kind of gate-way 



NUTRITION. 



23 



Fig. 7. 



from the mouth into the Pharynx. This is a funnel- 
shaped, muscular sack, covered on the inner surface 
with a continuation of the mucous membrane of the 
mouth. 

The pharynx is a kind of common chamber, commu- 
nicating with the mouth through the fauces, and with 
the nose by two passages called the pos- 
terior nares; with the ears, by two small 
funnel-shaped openings called the Eusta- 
chian tubes; with the Larynx, or voice- 
box, by the glottis, which is closed by a 
firm valve called the epiglottis, that 
shuts down on it, and over which the 
food is carried to the opening at the 
small end of the funnel, where it termi- 
nates in the CEsophagus, or gullet. 



27. (Esophagus — its structure and 
function. — The (Esophagus is a tube ex- 
tending from the pharynx to the stomach, 
and lies directly back of the windpipe. 
It is made of two coat§ or layers — an in- 
ner covering of mucous membrane, con- 
tinued downward from the mouth through 
the pharynx, and an outer muscular coat 
composed of a layer of fibers running 
lengthwise, and a double set of fibers run- 
ning spirally around the tube in each direction, and 
consequently crossing each other. The longitudinal 
fibers serve to hold the tube steady in the act of swal- 
lowing; while the oblique fibers, contracting behind the 
little ball of food, partly close the tube, and, the closure 

extending downward, carries it to the stomach. 
B. P.— 3. 



a. Oblique fibers. 

b. Longitudinal 
fibers exposed. 



24 



PHYSIOLOGY. 



Recapitulation. 

Nutrition is that function which supplies the material for the 
growth of the body, and to repair its wastes; including, also, 
the material for the production of animal heat. This material 
is called food, and is divided into the albuminate and carbon- 
aceous classes. Mastication, the first act of nutrition, is per- 
formed in the mouth, and consists in grinding the food and 
mixing it with saliva. The principal organs concerned in this 
are the teeth and the salivary glands. 

The pharynx receives the masticated food and passes it into 
the oesophagus, by which it is transmitted to the stomach. 



LESSON IV. 



Fig. 8.— The Stomach. 



DIGESTION. 

28. Anatomy of the Stomach. — The Stomach, into 

which the oesophagus carries 
the food, is a curved sack or 
bag, lying obliquely across the 
body immediately below the 
diaphragm, which is a kind 
of partition separating the 
cavity of the chest or thorax 
above, from the abdomen be- 
low 7 . The larger end of the 
stomach lies in the left side, 
and its greater curvature or 
rounded side is below. 

On the upper or concave 
side, a little nearer the left end of the stomach than the 
right, the oesophagus enters it. This is called the Cardiac 




a. Cardiac orifice, b. Pyloric ori- 
fice, c. Pancreatic duct. 



DIGESTION. 25 

orifice. Toward its righl extremity the stomach be- 
comes narrow, and finally passes into the intestines. At 
this point there is a band of muscular fibers, which are 
capable of contracting so as to close the opening entirely. 

This is called the Pyloric orifice. 

29. Functions of the Stomach. — The stomach is 

composed of three coats. The inner cr mucous coat is 
a continuation of that of the oesophagus, though differ- 
ing from it in many particulars. It is very delicate and 
soft like velvet, and besides thj little mucous glands or 
follicles it has a number of more complicated glands, 
whose mouths, opening on its surface, throw into the 
stomach a thin acid-fluid (the gastric juice) as often as 
food is taken. This gastric fluid, besides the acids dis- 
solved in it, contains also a peculiar substance called 
which, with the aid of a uniform heat, enables it 
to dissolve albuminate food. 

30. Muscular and Peritoneal Coats of the Stomacho 

— The second coat of the stomach is a strong, muscular 
envelope, consisting of two sets of fibers — one running 
from end to end of the organ, and another running around 
it. and crossing the first nearly at right angles. The third 
coat of the stomach is a serous membrane — smooth and 
dense — it being a continuation of th: Peritoneum, which 
membrane lines the whole cavity of the abdomen, and 
covers all the organs contained in it. This covering is 
reflected off from the lower surface of the diaphragm to 
the outer surface of the stomach, at the point where 
the oesophagus passes through that partition. 

31. Process of Digestion. — A strong sympathy exists 

between the mouth and the stomach, for as soon as mas- 
tication commences, and the salivary glands begin to act 



26 PHYSIOLOGY. 

freely, the peptic glands of the stomach pour out, at 
their numerous mouths, the gastric juice, ready to re- 
ceive the food when it arrives. 

As soon as this reaches the stomach, the muscular 
coats of that organ begin to contract, gently rolling the 
food from side to side, thus mixing it thoroughly with 
the gastric fluid constantly exuding from the inner coat 
of the stomach. In the meantime, the salivary glands 
are actively furnishing saliva, which is slowly convert- 
ing the starchy part of the food into sugar, and thus 
dissolving it. 

32. Formation of Chyme. — This action of the sali- 
vary glands has more of importance than is usually 
attached to it. The poisoning of the saliva by a quid 
of tobacco or a cigar, thus interfering with an important 
part of the process of digestion, is one of the fruitful 
sources of dyspepsia, however little the unfortunate vic- 
tim may suspect it. 

The digestive action continues from two to four 
hours, according to the nature of the food, the healthy 
condition of the organs engaged in the work, and the 
general vigor and activity of the body. The food thus 
acted on becomes a semi-fluid mass, nearly of a uni- 
form character, however various and unlike the original 
material may have been. This substance, called Chyme, 
is now ready to be passed through the pylorus into 
the intestines, where it enters on the third and last 
stage of digestion. 

33. Anatomy of the Intestinal Canal. — The Intes- 
tinal canal is a tube, varying in length from twenty- 
five to thirty feet, or even more than this in some 
individuals. This tube is divided into two sections, 



DIGESTION. 



27 



the small intestines and the Large. The first section, 
or small intestines, are divided, for the sake of con- 
venience in describing them, into three portions, called 
the Duodenum, Jejunum, and Ileum. 

The canal, in all its parts, has an inner mucous 
membrane, a middle muscular coat, much thinner than 
that of the stomach, and an outer covering of serous 
membrane, the peritoneum, it being a continuation of 
that which covers the stomach. 



-This peritoneal cover- 



Mesbntery and Lacteals. 



34. Lacteals and Mesentery 

ing is reflected off 
from the back part 
of the tube, in its 
whole length, form- 
ing a double -fold 
of the membrane 
called the Mesen- 
tery, which binds 
the whole intesti- 
nal apparatus firm- 
ly to the posterior 
wall of the abdo- 
men. The space 
between these folds 
of the peritoneum, 
forming the mesen- 
tery, is filled with a. Small intestines, b. Lacteals. c. Mesen- 

a net-work of blood- teric glands - * JIe * e » tei >-- * Lymphatic 

vessels. /. Thoracic duct. g. Aorta. 

vessels, nerves, and 

a class of vessels called Lacteals. These vessels, com- 
municating with the mucous surface of the intestines, 
carry a milky fluid containing the nutritious part of 




1 a 



28 



PHYSIOLOGY. 



the food in a dissolved state. The lacteals, in their 
passage through the mesentery, form clusters called 
mesenteric glands, in which the lacteal fluid undergoes 
an important change, by which it acquires many of 
the properties of blood. 

35. Colon and Xleo-colic Valve. — The large intest- 
ines differ materially in their form from the small. 
There are contractions at short intervals, diminishing 
the size of the tube at those points, and forming an 
enlargement or kind of cell between them. The small 
intestines do not enter the large tube in a continuous 
line, but appear as if the ileum was spliced on the side 
of the large intestine, at a point three or four inches 
from its end. At this junction the lips of the open- 
ing are elongated inward, so as to form a very perfect 
valve, which permits the contents of the small in- 
testines to pass into the large, 
but arrests all passage in the 
opposite direction. This is 
the Ileo-colic valve. 



6, 



a 



a. Ileum. 6. The valve, c. As- 
cending colon, d. Opening of sections 
appendix. 



Fig. 10.— Ileo-coiLic Valve. 




36. Direction of the Co- 
lon. — The closed end of the 
intestine lying back of this 
valve is called the Caecum, 
and that portion which lies 
forward of it is the Colon. 
This is divided into three 
the ascending co- 
lon, rising on the right side 
nearly to the stomach; the transverse colon, extend- 
ing across the abdomen below the stomach; and the 
descending colon, passing down the left side to the 




DIGESTION. 29 

rectum, which is the last division of the large intes- 
tines, and the termination of the intestinal canal. 

Fia. 11.— Intestinal canal. 

e a 

\ 



a. Duodenum, b. Ileum, c. Caecum, d. Ascending colon, e. Transverse 
colon. /. Descending colon, g. Rectum, h. Vermiform appendix. 

37. The Liver — its function. — The Liver, the largest 
gland of the body, is situated immediately below the 
diaphragm, and chiefly on the right side of the body. 
Its office (which will be more particularly described 
hereafter) is to separate from the blood a slightly tena- 
cious yellow fluid, called bile, which is collected into 
the gall bladder, and from thence passed into the duo- 
denum, a short distance below the stomach. 

The Pancreas is a long, slender gland, lying under 
the convex surface of the stomach, and secreting . a 



30 



PHYSIOLOGY. 



fluid very nearly resembling saliva, which it throws 
into the duodenum. 



Fig. 12.— The Ltver. 



a f£ 




a. Right lobe of the liver, b. Left lobe. c. Vena cava. d. Gall bladder. 
e. Portal vein. /. Bile duct. g. Hepatic artery. 

38. Digestive Process. The Spleen. — The food 
being converted into chyme in the stomach, and 
passed through the pylorus into the duodenum, is 
mixed with the pancreatic fluid which serves to di- 
lute it, and perhaps complete the work of the saliva 
in converting the starch into sugar. The bile being 
alkaline, from the soda which it contains, neutralizes 
any acid which the chyme may have brought from 
the stomach; and it also has an effect on the oily 
portions of the food, so as to make them dissolve 
readily. 

These changes convert the chyme into chyle, which, 
as a milky fluid, is absorbed by the lacteal vessels, 
and transmitted through the mesenteric glands into 
the Thoracic duct, which is the common trunk of all 
the iacteals. This vessel carries the lacteal fluid up- 
ward, and pours it into the large vein which returns 
the blood from the left arm. A little to the left, and 



CIRCULATION. 31 

below the great curvature of the stomach, lies the 
Spleen. It is made up chiefly of a net-work of blood- 
vessels. Its use, in the animal economy, has not been 
clearly determined. 

Recapitulation. 

The stomach is composed of three coats : an inner mucous coat, 
a middle muscular layer, and an outer serous membrane. The 
function of the stomach is to change the various forms of food 
into a homogeneous mass, and to render it soluble in water. 
This semi-fluid mass is called chyme. The intestinal canal is 
divided into two sections — the large and the small intestines. 
The mesentery, a double fold of the peritoneum, binds the in- 
testines to the posterior wail of the abdomen, and contains the 
lacteal vessels between its folds. The liver secretes bile, which 
acting on the chyme, converts it into chyle. 



LESSON V. 



CIRCULATION. 



39. The Apparatus of the Circulation. — Having, 
in the last lesson, followed the food through the first 
stage of preparation for nutrition, we now find it, if 
the work of digestion has been well done, prepared to 
enter the circulation, that it may be carried to all 
parts of the living body — to supply material for its 
growth in early life, and its repair at all times. This 
work of distributing the nutriment prepared by the 
changes it has undergone in the mouth, stomach, and 
intestines, to become a part of the living tissues, is 
performed by the Heart, Arteries, Capillaries, and Veins. 



32 PHYSIOLOGY. 

The heart consists of a right and left side, separated 
from each other by a strong partition, which, after 
birth, is entirely closed, so that there is no more com- 
munication between the right' and left cavity than if 
the two sides were distinct and separate hearts. 

40. Anatomy of the Heart. — Each side is composed 
of two chambers or cavities, capable of holding about 
two ounces of blood eacji. The first or upper one of 
these chambers is called the Auricle, and the lower one 
the Ventricle; and the two auricles and ventricles 
are distinguished from each other by the terms right 
and left. The right side of the heart receives the 
blood returning from all parts of the body, and sends 
it to the lungs to be purified and materially changed, 
from whence it is returned to the left side of the 
heart to be distributed again throughout the system. 

The lungs being near by the heart, the right side 
has much the lighter task, though the quantity of 
blood sent out from each side, in a given time, is the 
same. From this cause the walls of the right side of 
the heart are much thinner than on the left. 

41. Position of the Heart. — The heart is situated 
in the lower part of the chest, between the folds of 
the partition separating the lungs from each other. It 
is a cone-shaped organ, with the base or large end di- 
rected upward and backward, pointing toward the 
right shoulder, while the apex or small eiid projects 
downward, forward, and to the left side. 

When in vigorous motion, the point of the heart 
strikes against the front wall of the chest, and can be 
felt distinctly near the fifth rib on the left side. Its 
under side rests on the arch of the diaphragm, which 



CIRCULATION. 



33 



separates the chest from the abdomen. The heart is 
inclosed in a membra nous sae called the pericardium, 

between the inner surface of which and the heart there 
is always a small quantity of water, which serves to 
protect the heart from the effect of blows on the chest, 
or sudden movements of the body. 

42. Action of the Heart. — The blood reaches the 

right auricle as it is returned 

n ,., . i i ji Fig. 13.— Front view of the 

from the veins; and by the „ 

contraction of the auricle, the 
venous blood is forced into the / 

ventricle, through three tri- |||i m^ r 

angular folds of a membrane. W^F~\m\^-"f 

These are called the Tricuspid e ~~~ %J. Jp 5 ^...^ 

valves, and they are so ar- e-^5 g5&----g 

ranged as to permit the blood c'-'tWr''^^^^^^^- J 
to pass freely toward the ven- |^W»^P^^^Sk 

tricle, but close so as to arrest ^"^ffl^O 

its passage in the opposite di- ^| 

rection. ' ^■S 

The ventricle being now a y " 

filled, contracts on its con- ^w^r 

tents, and the blood is forced «• RigM ventricle. fc.Leftven- 

tricle. c. Right auricle, d. 

into the Pulmonary artery, Len auricle> 6j Cj 6j e< Pul . 

by which it is carried to the monary veins. /. Pulmo- 

1 A r, *xi i nary artery, a. Aorta, h. 

lungs. After passing the pul- * J 

monary capillaries, and under- 
going a change of which we shall speak in the proper 
place, it is returned to the heart by the pulmonary 
veins. 

43. Valves of the Heart and their use. — Entering 
the left auricle, the blood is transmitted through the 



34 



PHYSIOLOGY. 




a. Left auricle, b. Right auricle. 
c. Left ventricle, d. Right ven- 
tricle. /. Mitral valves, g. Tri- 
cuspid valves. 



valves, which, on this side of the heart, consist of two 

membranous folds called 

Fig. 14.— Valves of the Heart. T\r-j. i i • ± xi i ju 

Mitral valves, into the left 

ventricle, whose walls con- 
sist of a firm and power- 
ful muscle. It is now con- 
tracted, and the blood, 
propelled with consider- 
able force, is thrown into 
a large tube called the 
Aorta. 

This tube may be taken 
as the representative of 
the whole class of blood- 
vessels whose office it is 
to carry the blood from the 
heart. They are called Arteries, while those vessels which 

return the blood to the 

Fig. 15.— Semi-lunar Valves. 
heart are named Veins. 

The blood having en- 
tered the aorta, is pre- 
vented from returning 
to the ventricle, when 
that cavity expands, by 
three folds of the inner 
coat of the artery, which 
from their shape are call- 
ed Semi-lunar valves. 
/ 44. Arteries, Capil- 
laries, and Veins — 
their anatomy. — The 
arteries are firm, elastic 
tubes, made of three coats. The external coat is of a 




a. A section of the aorta laid open. 
b. The semi-lunar valves. 



CIKCULATION. 35 

spongy, cellular texture; the middle coat is of very dense, 
fibrous material, generally regarded as muscular; the 
inner coat is x smooth and very fine serous mem- 
brane, being a continuation, from the heart, of the 
lining membrane of the ventricle. The aorta sends off 
branches to all the living organs of the body; even 
the heart itself receives a pair of arteries from the 
aorta, to carry to it material for its repair. 

These branches, as they divide and sub-divide, grow 
constantly smaller, but more numerous, till at last they 
terminate in a net-work of hair-like vessels, called 
Capillaries, almost infinite in number. These vessels 
give origin to the system of veins which, running into 
each other, become less and less numerous, till finally 
they form one great trunk, the Vena Cava, through 
which all the veins of the general circulation com- 
municate with the heart. 

45. Forces concerned in the Circulation. — Several 
forces are concerned in the circulation of the blood, the 
first and chief of which is the contraction and expan- 
sion of the heart. Though the heart is a double organ, 
and concerned in carrying on two distinct circulations 
— one to the lungs and the other to the general sys- 
tem — yet all its parts work in concert. 

The two auricles contract at one time, and while 
they are contracting, the ventricle is expanded on each 
side; but as soon as these are filled with blood, they 
begin to close the cavity, and, by a powerful contrac- 
tion, the contents of each ventricle is injected into the 
artery united with it. While this is going on, the 
auricles are expanded to receive the constant stream 
of blood returned by the great veins. 



36 PHYSIOLOGY. 

46. The Pulse. — Each contraction of the ventricle 

gives a wave-like motion to the blood in the arteries. 
This is the Pulse. It is probably assisted by a con- 
traction of the artery itself, following directly after the 
wave of blood. The changes which are made in the 
condition of the blood while passing through the capil- 
laries, evidently exert a force in transmitting it through 
these minute passages. This force is entirely independ- 
ent of the contraction of the heart. The blood is thus 
constantly forced into the veins; these vessels, being 
filled, must overflow into the right auricle. The veins 
are passive in the work of circulation. 

Recapitulation. 

The circulation is carried on by the heart, arteries, veins, and 
capillaries. The heart is a double organ, consisting of a right 
and left side, and each side is composed of an auricle and a 
ventricle. The heart is inclosed in a sac — the pericardium — 
and lies in the partition separating the lungs, its larger end 
looking upward and backward, and its smaller downward and 
forward. Valves are interposed between the auricles and ven- 
tricles on each side of the heart. The arteries convey the 
blood from the heart, and the veins return it to that organ. 
The capillaries unite the arteries with the veins. The con- 
traction and expansion of the heart is the chief force concerned 
in the arterial circulation. 



LESSON VI- 



CIRCULATION. — CONTINUED. 



47. Teins — their Valves. — The veins originating in 
the net-work of capillaries, and joining together, form 



CIRCULATION. 37 

constantly enlarging trunks; but these, unlike the ar- 
teries, are soft and easily compressed. The middle or 

fibrous coat is almost entirely wanting, and the two 
remaining coats are much thinner than those of the 
arteries. When emptied of their contents, the arteries 

main open tubes; but the veins, under similar circum- 
stances, collapse — the walls falling in on each other. 

At irregular intervals, the internal coat of the veins 
forms pouches or folds, which operate most 
effectually as valves. They are so ar- FlG - 16 ~ valves 
ranged that the open end of the pouch 
is turned toward the heart, and when 
the blood flows in that direction, the 
valve closes down against the wall of 
the vein; but an attempt to force a flow 
in the opposite direction, fills the pouch 
with blood, and, by its enlargement, 
closes the vein completely. 

48. Venous Circulation effected by a ' A vehl laid 

open, exposing 

Muscular Movements. — The veins being the valves, 
soft, and passing freely through and 
among the moving machinery of the body, are con- 
stantly compressed by these movements, and the valves 
preventing this compression from forcing the blood 
backward into the capillaries, become material aids in 
transmitting the blood through the veins. 

It is sometimes important to be able to distinguish 
a vein from an artery at once. When the vessel is 
opened and blood is issuing from it — if it be an artery, 
it will flow in intermittent jets corresponding to the pul- 
sations of the heart; if it be a vein, the flow will be a 
constant stream. If the vessel be not opened, the pulsat- 




38 PHYSIOLOGY. 

ing motion may be seen or felt even in a small artery, 
but in a vein no such movement is perceptible. 

49. Lymphatic Vessels— their functions.— There is 

another class of vessels, called Lymphatics, which 

perform an important office in the circulation. They 

resemble small veins in their general 

fig. 17.— a lym- s t ruc t ure but carry a transparent fluid 
phatic Vessel # ' . 

magnified. instead of blood. Their valves are more 

numerous than those of the veins, and the 
small tubes show but little disposition to 
unite, often running jDarallel with each 
other, in clusters, for some distance. In 
some parts of the body, as about the neck, 
groins, and armpits, the lymphatics form 
numerous clusters or balls, called lym- 
phatic glands. These are the principal 
seat of scrofulous diseases. In their struct- 
ure they are much like the mesenteric 
glands. 

The lymphatics are chiefly employed 
in taking up and conveying to the blood- 
vessels the waste matter resulting from 
the constant wear of the tissues. They all communi- 
cate with the venous side of the circulation, so that 
the blood with which the lymphatic circulation is 
mingled is not sent out into the general circulation 
till it has been purified in the lungs. No lymphatics 
have } r et been detected in the brain, in tendon, carti- 
lage, or bone. In these tissues the office of the lym- 
phatics is probably performed by veins. The lacteals, 
in their general character and work, very much re- 
semble lymphatics. 



CIRCULATION. 39 

50. Absorbents — their action. — A class of lym- 
phatic vessels, called Absorbents, are engaged in the 
business of taking up Quids from the external surface 
of the body, and the surface of internal cavities. Vari- 
ous kinds of liquids, when applied to the skin, can be 
detected in the circulation, and in the different secre- 
tions, in a very short time. In the same manner, sub- 
stances inhaled are taken up by the absorbents, and 
carried directly into the blood-vessels, to be mingled 
with all the fluids of the body. In this manner poisons 
are often imbibed and diseases contracted, without the 
slightest suspicion of the manner of taking the poison. 

51. Absorbents in Serous Membranes. — Another 
office of the absorbent vessels is to take up and carry 
away the fluids constantly exhaled from the surface of 
membranes lining cavities. There is, in a healthy state 
of these serous membranes, a very nice adjustment in 
the w r ork done by the exhalent and absorbent vessels, so 
as to keep the surface constantly moistened, and yet suf- 
fer no accumulations of fluids in such cavities. Dropsy 
is but the disturbance of this nicely balanced exhala- 
tion and absorption. 

Simple fluids, like water, are not subject to any 
change in the stomach, nor do they take the circuitous 
route, by w r ay of the lacteals and thoracic duct, to the 
circulation, but are absorbed directly from the surface 
of the stomach, and pass into the veins at once. Even 
alcohol or turpentine, taken into the stomach, can be 
detected in the air breathed from the lungs, in a very 
short time after it is swallowed. 

52. Anastomosing Vessels. — The vessels constituting 
the circulatory apparatus, whether arteries, veins, capil- 

B. P.— 4. 



40 PHYSIOLOGY. 

laries, or lymphatics, often communicate by collateral 
branches, but always with vessels of their own kind. 

By means of these vessels, called Anastomosing 
branches, the surgeon is able to preserve the life of a 
part, though he may be required to tie the principal 
artery supplying that part with blood. An anastomos- 
ing branch, connecting the injured vessel below the 
ligature with a neighboring artery, will furnish a 
partial supply of blood ; and becoming enlarged by the 
increased work it is required to do, the anastomosing 
vessel soon acquires the capacity of the original trunk, 
and performs its office effectually. 

Recapitulation. 

The heart is a double organ, carrying on two circulations at the 
same time. 

The right side of the heart is devoted to the pulmonary circula- 
tion, or that carried on through the lungs for the purpose of puri- 
fying and oxidizing the blood. 

The left side of the heart is engaged in the distribution of the 
blood to all parts of the body, for its nutrition. 

In health the heart makes about seventy-five contractions in 
a minute. 

Arteries carry the blood from the heart — veins return it to that 
organ. 

Capillaries connect the extremities of the arterial and venous 
circulations; hence all arteries terminate in capillaries, and all 
veins have their origin there. 

The change from arterial to venous blood takes place in the 
capillaries of the general circulation, and the opposite change in 
the capillaries of the pulmonary circulation. 



RESPIBATION. 41 



LESSON VII. 

RESPIRATION. 

53. The Respiratory Organs and their use. — The 
3piratory apparatus consists of a trachea or wind- 
pipe, two lungs, the bronchial tubes, and air-cells. 
Auxiliary to these are the ribs, and the muscles be- 
tween them; the diaphragm, and the abdominal mus- 
cles. The purpose of this rather complicated apparatus 
is two-fold: first, to impart to the blood oxygen, which 
is one of the constituents of the air; and, second, to 
relieve the blood of carbonic acid and watery vapor, 
which it has acquired in passing through the capilla- 
ries, and which has resulted from the decomposition of 
the worn-out particles of the body and of the carbona- 
ceous food. 

54. Position of the Lungs. — The body or trunk is 
divided into two great cavities. In the abdomen or 
lower one of these is placed the digestive apparatus, 
which we have already described. The upper one is 
devoted to the Heart and great blood-vessels, which are 
situated in the space between the walls of a double 
partition that completely separates the cavity into 
two apartments; and to the Lungs, one of which fills 
each of these apartments. This cavity is called the 
Thorax or Chest. Unlike the abdomen, it is surrounded 
by bony walls on all sides, except the bottom, where 
it is separated from the abdomen by the diaphragm. 
The natural shape of the chest is that of a cone, with 
its small end upward, and its base resting on the dia- 
phragm below. 



42 



PHYSIOLOGY. 



Fig. 18.— Respiratory Apparatus. 



,,a 



55. Trachea and Bronchia. — The Trachea is a tube 
extending from the air-passages of the nose and the 
mouth to a point nearly opposite the top of the breast- 
bone, where it separates into two branches, which, 
from this point, take the name of Bronchia. These 
bronchial tubes divide and sub-divide as they distribute 
themselves through the lungs — each tube finally ter- 
minating in a little 
sac called an air-cell. 
These tubes, both the 
trachea and bronchia, 
are composed of rings 
formed of a hard, elas- 
tic substance, called 
cartilage. In the tra- 
chea the rings are not 
quite closed on the 
back part, thus leav- 
ing a soft side to 
the tube for the ac- 
commodation of the 
sesophagus, which 
lies immediately be- 
hind it. 

56. Air-Cells and their use. — The trachea and 
bronchial tubes are lined with a very delicate mucous 
membrane, which is extended into the air-cells. On 
this membrane, forming the inner surface of the air- 
cells, is spread out a net- work of capillary vessels — 
the terminations of the pulmonary artery. This mem- 
brane permits gases to pass through it readily, and 
thus the oxygen from the air in the air-cells is trans- 
mitted to the blood; and the carbonic acid contained 




a. Larynx, b. Trachea, c. Left lung. 
d. Right lung. e. Heart. 



RESPIRATION. 



43 



Fig. 19.— A m -cells. 



in the blood-vessels passes in the opposite direction, 
and escapes with the air exhaled from the lungs. 

Pure air is nearly one-lift li oxy- 
gen, and four-fifths nitrogen. These 

Liases are not chemically combined, 

but are merely in a state of mix- 
ture. When the air is taken into 
the lungs, it contains about twenty- 
one per cent of oxygen, but it 
is returned with but about seven- 
teen per cent ; the loss, however, 
is filled by nearly four per cent of carbonic acid and 

Fig. 20.— Diaphragm. 





c — 



a, a. Cavity of the right and left lungs, b, b. Ends of the ribs, which 
are removed to expose the diaphragm, c, c. Arch of the diaphragm. 

watery vapor. This proportion varies a little in dif- 
ferent individuals, and in the same individual in 



44 PHYSIOLOGY. 

different states of health; but this is about the average 
result in a healthy person. 

57. Mechanism of Respiration, Diaphragm. — In 

the act of breathing, the lungs are passive, the air 
being drawn in by the enlargement of the chest, made 
by the action of the Diaphragm and the muscles be- 
tween the ribs. 

The diaphragm is the floor of the chest. It is com- 
posed of at least two layers of muscles, covered on its 
under side by the peritoneum, and above by the pleura, 
a serous membrane lining the cavity of the chest, and 
covering the lungs. The diaphragm has nearly the 
shape of an inverted basin, being an irregular arch in 
every direction. When the muscles composing the dia- 
phragm contract, the arch is shortened, and conse- 
quently the crown of it is drawn downward, and the 
cavity of the chest made deeper in proportion. 

Fig. 21.— Intercostal, Muscles. 



a- 





a. External iniercostals. b. Internal intercostals. 

58. Ribs and Intercostal Muscles. — The ribs are 
articulated to the spinal column by a movable joint, 
and in front they are attached to the breast-bone by 
a flexible cartilage. They are curved around the body 



RESPIRATION. 45 

like a hoop; but they arc also bent downward from 
the back and to a little beyond the middle of the rib, 
from which they ascend to the breast-bone. The space 
between the ribs is filled by two layers of muscles, 
passing obliquely from one rib to the other. They 
arc called the external and internal intercostals. 

The upper rib, being nearly immovable, acts as a 
fixed point to which the whole series is attached by 
means of the intercostal muscles. And when these 
contract, the middle of each rib is drawn upward, and 
consequently the chest is enlarged in its transverse 
diameter. 

59. How we Breathe. — Now, as the lungs completely 
fill the cavity they each occupy, and the fold of the 
pleura covering the lungs, and that lining the chest, 
are in actual contact, it follows that the increased space 
made by enlarging the cavity of the chest, can be 
filled only by the air passing into the air-cells, and thus 
enlarging the lungs sufficiently to fill the enlarged cav- 
ities they occupy. By this movement, about twenty- 
five cubic inches of air are drawn in at an ordinary 
respiration. 

But a healthy pair of lungs will contain, in common 
breathing, about two hundred cubic inches of air, so 
that only about one-eighth of it is changed at each 
breath. The relaxation of the diaphragm and inter- 
costal muscles, though necessary for the expulsion of 
the air inhaled, is not of itself depended on in the 
economy of respiration. From the arch of the large 
bone on each side, which forms the basin-like cavity 
terminating the abdomen below, there arise several 
muscles which form the walls of that cavity. A pair 



46 PHYSIOLOGY. 

of these are attached, above, to the ribs, and, on con- 
tracting, draw these downward. Other muscles run 
transversely or obliquely around the abdomen, which, 
by their contraction, force the contents of the abdomen 
upward, and thus elevate the arch of the diaphragm, 
and expel the air inhaled. 

Recapitulation. 

Eespiration is carried on by means of the trachea and lungs. 
The lungs consist chiefly of bronchial tubes, air-cells, and 
blood-vessels. The ribs and their muscles, the diaphragm and 
the abdominal muscles, give the movements in breathing. The 
lungs are entirely separated by a double partition. Eespiration 
supplies oxygen to the blood, and removes impurities from it. 
These changes take place in the air-cells. The cavities contain- 
ing the lungs are enlarged by the contraction of the diaphragm 
depressing its arch, and by the elevation of the ribs increasing 
the lateral dimensions. The space thus made is filled by air 
passing through the trachea and bronchia. The contraction of 
the abdominal muscles elevates the arch of the diaphragm, and 
thus expels the air. 



LESSON VIII. 

RESPIRATION — PURIFICATION OF THE BLOOD. 

60. Two-fold Purpose of Respiration. — Respiration 
serves a two-fold purpose in the animal economy. First, 
it furnishes oxygen to the blood. This is carried by 
the circulation to all the tissues of the body, where it 
combines with the elements of the old and worn-out 
particles, forming with them new compounds, capable 
of being dissolved in the blood and thus carried for- 
ward into the veins. At the same time, in the capil- 
laries, it comes into close contact with the carbonace- 



RESPIRATION. 47 

ous elements of the newly digested food, combines with 
its carbon, forming carbonic acid, disengaging its other 
elements to form water. From these changes the heat 
of the body is supplied and maintained. 

But these products, resulting from the combination 
of the oxygen with the tissues and with the food, 
being thrown into the circulation, load the blood with 
impurities. The second purpose of respiration is to 
relieve the blood of these impurities. All the carbonic 
acid generated in the living body, and a large portion 
of watery vapor, as well as numerous other substances 
which find their way into the circulation and are in- 
capable of being made^a part of the living body, are 
discharged by the lungs. 

61. Chemical Changes — the Source of Animal 

Heat. — The production of heat by the chemical 
changes constantly taking place in animal bodies, 
appears to be intimately connected w r ith the evolution 
and expenditure of force in the body. Every move- 
ment of the body, or any part of it, requires a certain 
amount of force to accomplish it, proportioned to the 
extent and violence of the movement; and, as many 
of these motions are constant, and all of them frequent, 
they demand a constant and uniform supply of this 
force. This they have in respiration and its results. 
Hence it follows, that as we increase the active exer- 
cise of the body, there is a corresponding increase of 
breathing ; and more oxygen being thus distributed to 
the tissues, more chemical action takes place, and from 
this heat and force are evolved. 

62. Products of Respiration. — But all this is con- 
suming both the tissues of the body and the carbon- 

B. P.— 5. 



48 PHYSIOLOGY. 

aceous elements of the food, and this waste must be 
supplied by additional food, consequently exercise in 
the open air increases the appetite, and invigorates 
all the vital functions, thus furnishing new material, 
well prepared to replace the worn-out particles of the 
tissues, and enabling the several organs, whose duty it 
is to carry off and dispose of the old matter, to do that 
work effectually. A large proportion of this waste is 
converted into carbonic acid, which is formed by the 
direct union of the oxygen inhaled, and the carbon of 
the tissues. This being carried to the lungs, escapes 
with the air exhaled in respiration. 

If we fill a vessel with clear lime-water, and, through 
a tube, blow our breath into it, we shall soon perceive it 
becoming milky from the carbonic acid of the breath 
combining with the lime. The hydrogen, another ele- 
ment of the worn-out particles, unites also with the 
oxygen communicated to the blood in breathing, and 
thus forms water, a great part of which is thrown 
off from the lungs as vapor. 

63. Other Means of Purifying the Blood —Other 
portions of this waste material, rendered fluid by com- 
bination with oxygen, are taken up by the absorbents, 
and carried into the circulation, from which they are 
separated by the process of secretion. This operation 
is performed by a class of organs called Glands. The 
largest gland of the body is the liver, whose duty it is 
to separate, from the venous blood circulating through 
it, a peculiar fluid, the bile, which, as we have learned 
(§ 38), performs an important office in the conversion 
of chyme into chyle. A large part of the bile, in per- 
forming this work, is itself changed into sugar, in 



RESPIRATION. 



49 



Fig. 22.—] 'ekspira tort 

( - I A \ DS. 

e e 



■a 
b 



which form it re-enters the circulation as a carbonace 
ous element of the blood. The 

remainder of the bile, which 
is incapable of this change, is 
passed oh* as excrement. 

The Skin is another impor- 
tant outlet of the wastes of 
the living body. A cluster of 
small glands forms the lower 
surface of the skin, and from 
each gland a small tube, called 
a perspiratory duct, winds its 
way in a spiral course through 
the skin to its external sur- 
face. The mouths of these 
form what are commonly call- 
ed the pores of the skin. The 
perspiration consists chiefly 
of water, with various saline 
matters dissolved in it. Under ordinary circumstances, 
it passes off in the form of vapor, and is called insen- 
sible perspiration^ because it is not observed; but when 
the secretion becomes more active, it is liquid, forming 
drops of sweat. 





d- 



a. Cuticle, b. Colored layer of 
the skio frete mucosum). c. 
True skin, d, d. Perspiratory 

glands. e, e. Perspiratory 
ducts. 



64. The Skin. Perspiratory and Oil Glands.— 

Another set of glands are located near the surface of 
the skin, smaller and much simpler than the perspira- 
tory glands. They are the oil glands, or sebaceous follicles, 
w T hich furnish oil to keep the surface of the skin soft 
and pliable. The kidneys also perform an important 
office in the work of purifying the blood. They are a 
pair of large glands, situated in the upper and back 



50 



PHYSIOLOGY. 



part of the abdomen, and are concerned in separating 
from the blood a peculiar substance called Urea, which 
is formed in the decomposition of the tissues. 



Fig. 23.— Oil Glands. 








a. Simple oil gland, b. Oil glands surrounding a hair. 

Through these various outlets we see what ample 
provision is made for purifying the blood, and remov- 
ing from the system the waste matter resulting from 
the tranformation of the tissues. No one of these or- 
gans can suspend action, or be impaired in its func- 
tions, without deranging the healthy condition of the 
whole vital machinery. 

65. Temperature Measured hy the Air Breathed, — 

But a result of respiration, no less curious than it is 
important, is that of enabling a living body to main- 
tain a nearly uniform heat independent of the tem- 
perature of the surrounding medium. It required many 
years of patient observation, and investigation, to reach 
the cause of this wonderful phenomenon, and even yet 
there is much connected with it that is but imper- 
fectly understood; enough however is known to satisfy 



K INSPIRATION. 51 

scientific men that, primarily, animal heat depends on 
respiration. 

Fishes, whose respiration is carried on by gills, ob- 
taining merely a portion of the oxygen which water 
is capable of absorbing, have a temperature but little 
above that of the water in which they live. Reptiles, 
breathing with membranous lungs, and inhaling but 
a small volume of air, and retaining but little of its 
oxygen, are cold-blooded animals, or nearly so. With 
them, breathing may be suspended for an hour or 
more, even while the animal is active; and when the 
temperature of the atmosphere falls to near the freez- 
ing point, respiration is suspended entirely and indef- 
initely, and the reptile remains torpid until the tem- 
perature rises again. 

68. Mean Temperature of the Body. Effect of 
Evaporation. — Among w r arm-blooded animals the tem- 
perature varies somewhat, but is always measured by 
the amount of oxygen consumed. In man, the tem- 
perature, in health, varies but little from ninety-eight 
degrees Fahr. ; in many of the inferior animals it falls 
below this; while in birds, it rises above one hundred 
degrees; but birds breathe more air, in proportion to 
their weight, than even man. The actual amount of 
air consumed in respiration is not to be measured by 
the number of cubic feet of air inhaled in a given time, 
as the volume of all gasses is materially increased by 
an elevation of temperature. 

A person, breathing an atmosphere at zero, will 
inhale a much greater quantity of air in the same 
volume than he will with the temperature at eighty 
degrees. This important provision materially aids in 



52 PHYSIOLOGY. 

maintaining the heat of the body in cold climates. The 
increased quantity of food required in the winter season, 
as well as the kind of food which the appetite de- 
mands, is a wise provision for accomplishing the same 
purpose. 

To modify the effects of a high temperature, the 
perspiratory function of the skin is the chief agent. 
Evaporation is a cooling process; when, therefore, the 
heat of the air approaches the natural temperature of 
the body, a copious evaporation from the skin relieves 
the heat. 

Recapitulation. 

Respiration furnishes the blood with oxygen, and carries off 
impurities; these changes are the source of animal heat. 

Secretion is performed by glands. The liver secretes bile. The 
cutaneous surface, prespiration. Oil glands. The kidneys sep- 
arate urea from the blood. 

Animal heat depends on respiration. Normal temperature of 
the human body is ninety-eight degrees, and is uniform in dif- 
ferent climates. 



LESSON IX, 



GROWTH AND REPAIR. 



67. Growth and Repair— why complex.— The im- 
mediate action of nutrition, that is, the original growth 
of all the parts of the body, and the repair of the 
constant waste which is the necessary result of every 
motion in the animal machine, is a very complicated 
process, and there is much about it which is but im- 
perfectly understood; much which the human mind 



GROWTH AND REPAIR. 53 

may never fully comprehend What is done, we know; 
and the general laws under which the great work of 
growth and of repair ia carried on, are understood in 

the main points relating to their practical application. 
From the very nature of the chemical and vital forces 
involved in this work, there must remain much that is 
unknown, perhaps unknowable. 

68. Composition of the Blood. — All the tissues of 
the body, from tlie tender and delicately organized 
brain to the most compact and solid bone, are formed 
from material taken into the body as food, digested in 
the stomach, dissolved in the blood, and from that fluid 

■united and built into its proper place, while that 
fluid is being transmitted through the capillaries. 
Healthy blood, on cooling, separates into a semi-solid 
substance called Coagulum, and a nearly transparent 
fluid, the Serum. This serum is the basis of the blood, 
and may be considered as water, holding the coagulum 
and several mineral substances in solution. 

In every one hundred parts of blood, there are 
seventy-nine parts water, and twenty-one parts of 
dry solids. These solids are dissolved in the serum, 
and held in that condition by the living state of the 
blood, and its constant motion. If the blood be drawn 
into a basin, though it be kept at the natural tem- 
perature of the body, yet it rapidly separates into 
coagulum and serum. 

69. Proportion of the Ingredients in the Blood.— 

The coagulum, if carefully washed in cold water, may be 
reduced to a white fibrous mass, much like muscles 
in composition and appearance. The matter which has 
been washed out is found to consist of a coloring sub- 



54 PHYSIOLOGY. 

stance rich in iron, from the oxide of which metal 
it has been supposed to derive its color. 

Of the twenty-one parts, in one hundred, of solid 
mr,£ter contained in healthy blood, about one-seventh 
is composed of saline matter, (chiefly common salt,) 
of fatty substance, and sugar; two-sevenths consist 
oi albumen, a substance like the white of an egg; 
and the remaining four-sevenths appear to be derived 
from the breaking down of minute disks, which the 
microscope reveals in great numbers in the blood. 

Fig. 24.— Blood Disks, 





a. Colored disks— various forms, b. Colorless disks— different 
appearances. 

70. Blood Disks — two kinds. — Of these disks, or 
corpuscles, as they are sometimes called, two kinds are 
observed in the blood of all animals which suckle 
their young, colored corpuscles and colorless ones. The 
colored corpuscles seen in the human blood, are small, 
circular bodies, flattened into thin plates or disks. 
The colorless corpuscles are more globular in form, 
and vary in number with the changing condition of 
the system. 

While the colored corpuscles appear to be a constit- 
uent part of the blood itself, those without color seem 
in some way intimately connected with the appropri- 
ation of nutriment to the growth and repair of the 
various organs. 



GROWTH AND KEPAIR. 55 

71. Cell Structure of the Tissues.— Among the as- 
tonishing revelations of the microscope, none is more 
marvelous than tin* truth thai all living forms, animal 
and vegetable, arc, in their ultimate structure, com- 
posed of cells. These cells, in their original form, are 
globular, or slightly elliptical, but when they are built 
into tissues, the pressure of the adjoining cells gives 
them a great variety of forms. Sometimes they adhere 
together like strings of beads, and form fibers, as in 
the muscular tissue; sometimes the cell-walls are ab- 
sorbed at the point of adhesion, and thus the fiber 
becomes a tube, as in the white matter of the brain; 
and again, the globular cell will assume strange and 
irregular forms, as seen in the gray matter of the 
brain. 

72. Cells — how formed and removed. — All the vari- 
ous tissues of the body are thus formed, and the original 
cells appear very much alike. They resemble little 
bladders or sacs, filled with a transparent fluid: but the 
cell-walls permit both fluids and gases to pass in and 
out of the cell readily, and by this means the cell be- 
comes filled with the proper material to form the differ- 
ent tissues of the body. Thus earthy matter, filling cells, 
forms solid bone; fibrine, in a like manner, forms muscle; 
and, in like manner, all the other tissues are formed. 

In the waste and repair of the tissues, the work on 
both sides proceeds by cells. In the activities of the 
system, the cells, one by one, are broken down, the 
material of which they were formed is taken up by 
the absorbents and conveyed to the proper organs to be 
disposed of, and instantly the place of each removed 
cell is occupied by a new and more vigorous one. 



56 PHYSIOLOGY. 

73. Modes of Cell Growth.— These cells, whether pro- 
duced in the fluids of the body, or in more intimate 
connection with the tissues, are always produced from 
a pre-existent cell. In the production of cells in veget- 
able growth, we have been able to examine the process 
much more clearly than is possible in the animal tis- 
sues. Here we learn that they multiply in several 
ways. An existing cell may become lengthened, and 
growing narrow in the middle, may assume the hour- 
glass form, and finally separate into a pair of inde- 
pendent cells; or cells may sprout from the opposite 
points of an existing cell, as from the poles of a globe, 
and, having attained their growth, disengage them- 
selves from the parent cell. 

In whatever way cells may be multiplied or produced, 
no well-established instance of the production of a ceil 
without direct connection with a pre-existing one has 
been placed on record. 

74. Life Force — its relation to Cell Destruction. — 

The transformation of the tissues by the removal of old 
cells, and the formation and deposition of new ones to 
supply their place, appears to be, in some way, inti- 
mately connected with the production and expenditure 
of force in the animal economy. Every movement of 
the body is accompanied with a correspondent waste 
of cells, and a proportional expenditure of force. We 
live by the death and renewal, one by one, of the 
cells composing the living machinery; and that ma- 
chinery is kept in working order only by being con- 
stantly renewed. To impair or disturb this destruction 
and renewal of the cell structure, is to produce disease, 
and to arrest it, is death. 



GROWTH AND REPAIR. 57 

75. The Blood the Agent of Cell Transformation.— 

The blood is the immediate instrument of this vital 
action. It conveys the prepared material for the new 
cells to the tissues where it is to be used, and removes 
the remains of the decomposed cells; and as these 
changes must be constant and unintermittent, that 
life may be maintained, so the blood must be kept 
in constant and incessant motion, that the cell trans- 
formation may not be interrupted. The pulsation of 
the arteries, measuring the circulation of the blood, 
becomes the most important index of the manner in 
which the life functions are being carried on at any 
given time. 

76. Quantity of Blood. — The quantity of blood cir- 
culating in the body is constantly changing, even in 
the same individual; and in different persons it varies 
with age, state of health, habits of life in regard to 
food, exercise, etc. As a general rule, it may be safe 
to estimate the quantity of blood at about one-tenth 
of the weight of the body. Its power to impart life 
to the tissues will depend much on its composition, 
and this will, to a great extent, be measured by the 
quality of food, and its perfect digestion. 

Recapitulation. 

Growth and repair are complex, and not fully understood. 
All parts of the body are repaired from the blood. Nature and 
substance of healthy blood. Blood disks are of two kinds. 

All animal and vegetable structures are composed of cells of 
various forms. Formation and removal of cells. Modes of their 
growth. Relation of the death and renewal of cells to life. 

Cells are built by the blood. The blood constitutes about 
one-tenth the weight of the body. 



58 



PHYSIOLOGY. 



LESSON X. 

SYSTEM OF VOLUNTARY MOTION. 

77. Bones — their use — how formed. — Having briefly 
considered the system of nutrition, in the several 
functions which contribute to carry on that work, 



Fig. 25.— Front view of the 
Skuletox. 



Fig. 26.— Back view of the 

Skelktun. 





we proceed to look at the system of voluntary motion. 
This consists of a number of Bones, so formed as to 



SYSTEM OF VOLUNTARY xMOTION. 50 

serve as solid levers of motion, or to act as a protec- 
tion from injury to the important and more delicate 
organs of the body. 

These bones are originally formed of an elastic, semi- 
solid substance called Cartilage. The earthy matter is 
afterward deposited in it, so as to give to bone the 
density and general character of a mineral substance. 
This process of changing cartilage to bone is called 
ossification. In the long bones, such as those of the 
limbs, ossification begins near the middle, and extends 
gradually toward the extremities, leaving a portion of 
the extreme end of the bone, which, except in very 
old persons, still remain cartilaginous. 

78. Composition of Bone. — The proportion of animal 
and earthy matter varies with the age of the person, 
with the diet, habits of life, etc. In childhood, the 
earthy matter forms about one-half the weight of the 
bone; in adult life, four-fifths; and in extreme old 
age, as much as nine-tenths. The hardness and brit- 
tleness of bone depends on the proportion of earthy 
matter. And hence the bones of old persons are easily 
fractured, and unite slowly when broken; on the other 
hand, the bones of children are readily bent or distorted 
by confinement in improper positions. 

The earthy matter of bone consists almost entirely 
of lime, in combination with phosphoric and carbonic 
acids, and, like every other part of the living body, 
is subject to the general law of removal and replace- 
ment; but the transformation goes on more slowly in 
the bones than in the softer tissues of the body. 

79. Structure of Bones. — Bones are covered with a 
dense fibrous membrane, called the Periosteum, from 



60 



PHYSIOLOGY. 



which they are supplied with nutritive vessels. In 
the long bones, the center of the bone is hollowed 
out, leaving a cavity which is filled with fatty 
matter called marrow. This marrow cavity does not 
extend entirely to the ends of the shaft, but its 
place is supplied by a porous structure, which not 
only fills the cavity, but expands the extremity of 
the bone, so as to furnish a greater bearing surface 
at the joints. The flat bones, such as those of the 
head, are composed of two plates of solid, 

Fig. 27 — Struo ,. t . , -i. , 

turk of the osseous matter, and an intermediate space 
long bonks, filled with a cellular, bony structure. 

80. Mechanism of the Long Bones. — 

Principles well known to mechanical phi- 
losophers are involved in this arrangement 
of bone material. Lightness is of great 
importance in a moving limb; but, at the 
same time, strength must be provided for 
in bones intended to sustain the weight 
of the body, and to afford attachment to 
powerful muscles which are to be the in- 
struments of complicated, vigorous, and 
rapid motions. In no other way could 
both these objects be secured so effectually, 

a, c. Spongy ex- 

tremitiesofthe as ®¥ making the shafts of the bones 

femur. hollow. 

. anow cay- -g^ a fi Tm articulation requires that 

ity in the shaft. 1 

the surfaces of the bones which bear on 
each other at the joints, should be broader than that 
which a cross section of the bone in the middle of 
the shaft wculd give. The spongy texture of the 
bones at their articulating ends, as seen in the long 




SYSTEM OF VOLUNTARY MOTION. 61 

hoaes of the limbs, admirably accomplish this purpose, 
without increasing the weight or diminishing the 
strength. 

81. Hones not Sensitive. — In a healthy condition, 

bones have no sensibility. When they become dis- 
eased, however, they are often acutely sensitive. The 
popular idea, that the marrow of a bone is very painful 
when touched, is altogether false. Marrow is simply fat 
deposited in the cavities of a spongy tissue. It receives 
nutriment by means of blood-vessels, which pass ob- 
liquely through the walls of the cavity at particular 
points, usually near the middle of the shaft. 

82. Articulations. — Bones are joined together by 
three kinds of union, to wit : joints, sutures, and 
symphyses. A Joint is the union of two bones, admit- 
ting of motion at the point of union. In the true 
joints, the ends of the bones are covered with a pad, or 
cushion of cartilage, which readily yields to pressure, 
and thus serves to break the concussion when the bones 
composing the joint are violently forced together, as in 
jumping or running. 

In youth, this cartilage is thick; but as age advances, 
ossification extends further toward the extremity of the 
bones; and in old persons, the cartilages of the joints 
are nearly obliterated. From this cause, old persons 
are cautious in all their movements, and carefully avoid 
leaping, or any other movement that might bring the 
ends of the bones violently together. 

83. Ligaments— their form and use. — The bones 
uniting with each ether in joints, have the surfaces 
which come together formed so as to fit very nicely T 
and they are held in place by bands of dense, fibrous 



62 PHYSIOLOGY. 

substance, so arranged as to admit of motion within 
a limited range. 

In the principal joints these bands, or ligaments, as 
they are called, are so connected as to form a continuous 
layer, completely surrounding the articulating extremi- 
ties of the bones, and thus inclosing the joint in a kind 
of' sac. This continuous band is called the Capsular lig- 
ament. The articulating surfaces of the bones, as well 
as the inner surface of the capsular ligament, is covered 
with a very fine, smooth membrane, from which is 
secreted a slimy fluid, that serves to lubricate the 
joint and prevent friction. This is the sjmovial fluid, 
commonly called "joint water." 

84. Kinds of Joints. — There are several forms of 
joints ; the most important, however, are the ball 
and socket and t]ie hinge joint. The first of these 
admits of motion in all directions, and is well illus- 
trated in the hip joint. In many respects, this is the 
most perfect articulation in the body. It allows a 
greater range of motion than any other ; has a deeper 
socket and a more perfect ball than is found elsewhere ; 
and it has, in addition to a most perfect capsular liga- 
ment, a strong cord binding the extremity of the ball 
to the bottom of the socket, thus securing a wide range 
of motion in all directions, and, at the same time, 
giving great strength to the parts. The hinge joint 
is well illustrated in the knee and elbow. It admits 
of motion but in one direction, or, rather, backward 
and forward on the same line. 

85. Irregular Joints. — At the wrist and ankle we 
have examples of compound joints, formed by the artic- 
ulation of a number of bones, so adjusted as to allow but 



SKELETON. 63 

little motion between any two bones, and yet the aggre- 
gate gives considerable motion in every direction. In 
the spinal column, or back-bone, Ave have still another 
contrivance for allowing motions, though there are no 
articulating surfaces between the several pieces of the 
column. An clastic cartilage is interposed between 
these pieces, adhering firmly to each, and thus, by 
compression and distention, furnishing a good degree 
of motion. Nearly akin to this is that kind of union 
between bones, called Symphysis, where two bones are 
joined by smooth edges, and held in place by a thin 
layer of cartilage interposed. This kind of union does 
not admit of motion. If the edges are indented, or 
dove-tailed into one another, and the cartilage omitted, 
the union is called a Suture. 

Recapitulation. 

Bones are formed from cartilage. Earthy matter forms from 
one-half to nine-tenths of the bones. They are covered by the 
periosteum, and contain marrow in central cavity. Form of bone 
best for strength and lightness. Bones are not sensitive. They 
are united by joints, sutures, and symphyses. Form and use of 
ligaments. Synovial fluid prevents friction. Varieties of joints, 
ball and socket, and hinge. Irregular forms. Symphysis and 
suture defined. 



LESSON XI. 



SKELETON. 



86. The Skeleton — its division. — The bones of th6 
body, arranged in their natural position, constitute a 
Skeleton. When the bones are held together by the 



B. P.— 6. 



64 



PHYSIOLOGY. 



ligaments, the group is called a natural skeleton; if 
these have been removed, and the bones are held in 
place by means of wires, it is an artificial skeleton. 

Anatomists usually enumerate two hundred and eight 
bones in the skeleton, not including the teeth. Some, 
however, reckon more, others less than this number, for 
reasons which will appear in the further description 
of the particular bones. For convenience of description, 
the skeleton is divided into four sections: 1st. Bones 
of the head ; 2d. Bones of the trunk ; 3d. Bones of the 
upper extremities; 4th. Bones of the lower extrem- 
ities. 

87. Bones of the Head. — The Head is divided into 
bones of the skull and of the face. The Skull, or cra- 
nium is composed of eight bones. The frontal bone 

Fig. 28.— Fiioxt view of Skull.. Fig. 29.— Base of the Skull. 

b-- ^mm^ .-6 

5-- 



a 




..d 




a. Frontal bone. b. Right parietal 
bone. c. Left parietal bone. d. 
Left temporal bone. 



a. Foramen magnum. 

b. Occipital bone. 

c. c. Zygomatic arch. 



occupies the region of the forehead. The side of the 
head has a pair of parietal bones in the upper region, 
and a pair of temporal bones below. The back part of 



SKELETON. 



66 



Fig. 30.— Vertical view of the 
Skull. 

a 



the head, and most of the base of the skull, is occupied 
by the occipital bone. In the forward part of the base 
of the skull are two small bones, the ethmoid and sphenoid, 
which are seen only by removing the upper part of the 
skull. 

88. The Cranial Arch— Bones of the Face. — The 
bones of the skull are joined firmly by sutures, and the 
shape of each bone is such as to present the form of an 
arch in whatever line it is 

measured; and the whole 
skull forms a dome, or 
arched roof of the chamber 
where the brain, the most 
important organ of the 
body, is carefully depos- 
ited. 

The bones of the skull 
are made of two plates, 
separated by a thin layer 
of spongy bone. By this 
arrangement the concus- 
sion, or jar of injuries re- 
ceived on the outer plate, 
is mainly arrested before 
it reaches the brain. The 
bones near the base of the 
skull are much thicker than those which form its sides 
and upper part. This serves as a solid abutment to the 
arch, to enable it to withstand severe blows on the top 
of the head, or to resist great pressure at that point. 
The Face is composed of fourteen bones. 

89. The Spinal Column. — The trunk is divided into 




. Frontal bone. &, b. Parietal 
bones, c. Occipital bone, d, d. 
Lambdoidal suture, e, e. Coronal 
suture. /. Sagittal suture. 



66 PHYSIOLOGY 

the thorax and the pelvis. These, with the soft parts 

connected, form two important cavities — the chest and 

the abdomen. The thorax consists 

H1G * ° ' of the spinal column, the ribs, and 

Spinal Column. r 

the sternum, or breast-bone. 

Cervical lg^ The Spinal column consists of 

Vertebra*. |||? twenty-four bones. Each bone is 

\3§S^ called a Vertebra. Seven of these 

lift?^ are in the neck (cervical vertebrae), 

WW twelve in the back (dorsal verte- 

Dorsal WKflte 

Vertebra. ^^£ brae), and five in the loins (lumbar 

S%^' vertebrae). Each vertebra consists 

(^§k of a body and seven projecting 

^^^^ bones, called processes. These pro- 

"i^^ff cesses unite at their base, so as to 

Lumbar ^^^> form a continuous tube for the 

Vertebra* I "''^felPllli . -i • « 

' ^K passage of the spinal cord. This 

^^^^ tube does not pass through the 

sl body of the vertebra, but lies just 

W back of it. 



Sacrum. 



90. Union of the Vertebrae. — The vertebrae are 
united together by a layer of cartilage which is 
firmly attached to each bone, and yet it has elasticity 
enough to admit of considerable motion; but the broad 
and strong band of ligaments which binds the articu- 
lating processes together, limits that motion, and renders 
the articulation more firm and secure than any other 
joint in the body. 

The spinal column, when viewed from the back, 
should present a straight line; but viewed laterally, 
it is slightly curved like the letter S. This form is a 
wise arrangement, serving to break the force of any 



SKELETON. 



67 



sudden jar of the body, and thus save the brain from 
the concussion. 



Fig. 32. a Lumbar Vertebra. 




a. Body of the vertebra. 6, b. Transverse processes, c, c. Articulating 
processes, d. Spinous process. 



-The Ribs form 



Fig. 33.— The Thorax. 



91. The Ribs— their articulation 

the side walls of the 
thorax. They are twen- 
ty-four in number — 
twelve on each side — 
and are divided into 
three classes. Seven are 
true ribs, three are false 
ribs, and two are float- 
ing ribs. Each rib has 
two curvatures — one 
which bends it around 
the chest horizontally, 
and another which gives 
it a downward curva- 
ture from the back for- 
ward. 

The ribs are united 
to the vertebrae by true 
joints, but forward, the true ribs join the breast-bone 




435 c ~ 

a. Sternum, b. Seven true ribs. c. 
Three false ribs. d. Two floating 
ribs. e. Dorsal portion of the spinal 
column. 



68 



PHYSIOLOGY. 



Fig. 34.— The Pklvis. 

a 



by flexible cartilages. The three false ribs unite to a 
cartilage which is common to all of them, and by 
means of which they are attached to the breast-bone. 
The floating ribs have no forward attachment. 

92, The Sternum. Bones of the Pelvis.— The Ster- 
num, or breast-bone, 
forms the front of the 
thorax. In infancy, 
it is in eight distinct 
pieces ; in youth, 
three ; and in old age, 
but one. It is the 
last bone in the body 
to ossify, and, except 
in extreme old age, 
the point at the lower 
end remains cartilagi- 
nous. 

The Pelvis, or lower 
division of the trunk, consists of four bones. The 
Sacrum, which forms the back part of the basin, appears 
like a continuation of the spinal column, only that the 
vertebrae are grown firmly together. At the extreme 
lower point of the sacrum is a small conical bone, called 
the Coccyx. On each side of the sacrum, and uniting 
with each other in front, is a large, irregular formed 
bone, called the Innominatum. In early life this is com- 
posed of three pieces, and it is often described as three 
distinct bones; but in adults they become completely 
united. 

93. Shoulder, Arm, Forearm, and Hand. — The 
upper extremity is divided into the shoulder, arm, fore- 




a. Sacrum, b, b. Right and left innom 
inatum. c. Coccyx. 



SKELETON. 



69 



Pig. 86.— Left Clavicle. 




a. Articulation with the acromion pro- 
cess of the scapula, b. Articulation 
with the sternum. 



Fig. 36.— Left Scapula. 

Jb 



arm, and hand. The shoulder consists of a large, triangu- 
lar bone, the Scapula, 
or shoulder-blade, and 
the Clavicle, or collar- 
bone, which is at- 
tached to the upper 
end of the sternum at 
one extremity, and to 
the scapula at the other. 

The arm has one bone, the Humerus, which is articu- 
lated, by a ball and 
socket joint, to the 
head of the scapula 
above, and to the 
bones of the forearm 
by a hinge joint be- 
low. The forearm 
consists of two bones, 
the Radius on the 
side of the arm cor- 
responding to the 
thumb, and the Ulna 
on the other side. 
The ulna forms the 
principal part of the 
elbow joint, but the 
radius gives the 
chief articulation at 
the wrist. 

Three groups of 
bones form the 
hand. The Carpus, 
or wrist, consists of eight bones; the Metacarpus, or 




a. Acromion process, b. Coracoid process. 
c. Spiue, or ridge on the back of the scap- 
ula, d. Articulation of the humerus. 



70 



PHYSIOLOGY. 



palm of the hand, has five bones ; and the fingers have 
three bones, or phalanges, in each; while the thumb 
has but two. 




Fig. 38.— Ulna 
and Radius. 



Fig. 39.— Carpus or 
Wrist. 



a. Shoulder artic- 
ulation. 

b. Elbow articula- 
tion. 




a. Elbow articula- 
tion. 

b. Wrist articula- 
tion. 




a. Carpus or wrist — eight 
bones, b. Metacarpal bones. 

c. Lower end of the Radius. 

d. The ulna. 



94. Bones of the Lower Extremities. — The lower 
extremity is divided into the thigh, leg, and foot. The 
Femur, or bone of the thigh, is the largest long bone of 
the body. At the upper end it has a head, which 
stands at an angle of about forty-five degrees with the 
shaft of the bone. This head is received into a deep 
cavity in the innominatum, and forms a complete ball 
and socket joint. The bones of the leg are the Tibia 
which articulates with the femur by a hinge joint ; the 
Fibula, a small bone placed on the outer side of the tibia 
as a kind of brace ; and the Patella, or knee-pan, a flat, 
oval-shaped bone, placed on the front of the knee joint 



SKELETON. 



71 



to serve as a kind of pulley. The foot consists of the 
Tarsus, or ankle, a group of seven bones: the Metatarsus, 




a Head of the femur. 
b. Articulating sur- 
face at knee joint. 



Fig. 41.— Tibia and Fig. 42.— Tarsus and 
Fibula. Metatarsus 



C. 




b 



a. Tibia, 6. Fibula, 
c. Knee joint. d. 
Ankle joint. 




a. Seven tarsal bones. 
6. Five metatarsal 
bones. 



or foot proper, with five bones and the toes, with three 
bones in each, save that the great toe has but two. 
Small bones, called Sesamoid bones, which are not enu- 
merated here, are frequently found near the joints. 



Recapitulation. 

Skeleton, natural or artificial, consists of two hundred and 
eight bones. The skull consists of eight bones joined by sut- 
ures, and consisting of two plates separated by spongy matter. 
The face is composed of fourteen bones. 

The thorax consists of spinal column, ribs and sternum. The 
spinal column consists of twenty-four bones united by layers of 
B. P.— 7. 



1 1 PHYSIOLOGY. 

cartilage. There are twenty-four ribs, all jointed to the spinal 
column, ten on each side joined to the sternum. 

The sternum consists of from one to eight bones. The pelvis 
consists of four lt)ones. The upper extremities consist of thirty- 
two bones each, the lower of thirty each. 



LESSON XII. 

MUSCLES. 

95. Muscles and their functions. — The bones, with 

their joints held firmly together by ligaments, and yet 

permitting much freedom of motion, are admirably 

adapted to the great variety of movements required 

to perform all the functions of the human body. But 

the bones have no power of motion; they are merely 

the machinery of motion, to be operated on directly by 

the muscles, and remotely 
Fig. 43.— Muscular Fibers as -, , n . 

SEEN BY A MICROSCOPE. ^ ^ ^VOllS System. 

Muscles are formed of nu- 
merous bundles of fleshy 
fibers, bound together by a 
firm membrane, called the 
Facia. The fibers of which 
a muscle is composed are 
exceedingly fine threads ; and yet the microscope reveals 
the fact that each fiber is composed of a string of cells 
slightly elliptical in form, and attached together by 
their longer axes. By changing the form of these cells 
so that they become more globular in shape, the fiber is 
made shorter ; and this change taking place at the same 
time in all the fibers of a muscle, the parts to which the 




MUSCLES. 



73 



Fig. 44.— Tendons of 
the Right Hand. 



a- 



two ends of the muscle are attached are drawn nearer 
together. This is muscular contraction. 

J)(>. Tendons; — their form and use. — The manner in 
which the will directs, and the extent to which it gov- 
erns this contraction and consequent 
motion, and the part which the 
brain and nerves perform in this 
work, will be explained when we 
come to study the Nervous System. 

The muscles which move the 
limbs, and perform the chief vol- 
untary movements, have various 
forms, generally swelling larger 
near the middle, and tapering 
toward the end where motion is ef- 
fected; they usually terminate in a 
dense, white cord called a Tendon. 
These tendons are sometimes very 
long, as, for example : the muscles 
which move the hand are situated 
on the forearm, just below the elbow, 
and their tendons are carried down 
over the wrist joint, and inserted 
into the bones of the hand and 
fingers. 



Mil 




a. Muscles which move 
the fingers, b. Ten- 
dons extending from 
the muscles to the 
fingers, c. Annular 
ligament. 



97. Union of Tendons with 
Muscles. — In this manner, symmetry and lightness is 
secured for the hand, while great variety and force give 
character to its motions. So, in other parts of the body^ 
the muscles are placed w r here they will be least in the 
way, and where they will most conduce to symmetry 
and beauty of form ; and the motion produced by their 



74 PHYSIOLOGY. 

contraction is conveyed by means of tendons to the 
point where it is to have its effect. 

The muscular and tendonous fibers interlock, so that 
it is impossible to say precisely where the muscle ends 
and the tendon begins ; yet the two kinds of fibers differ 
materially. The fibers forming the tendonous cords are 
very fine, hard, inelastic, and strong ; and though the 
muscles are so much larger than the tendons, yet a 
sufficient force applied will tear the muscle in two 
before the tendon will break. Where the tendons are 
attached to bones, the fibers penetrate the solid bone, 
and hold very firmly. 

98. Arrangement of Muscles in producing Motion. — 

The broad, flat muscles, such as form the walls of the 
abdomen, etc., commonly have a tendon on one side, 
into which the muscular fibers are inserted; or a ten- 
donous band passes through the middle, into which the 
fibers run obliquely on each side. 

The most common arrangement for motion is where 
each end of a muscle is inserted into a different bone, 
and these united by a movable joint. In this arrange- 
ment, the muscle is situated oh the fixed part, or that 
which does not move, and the motion is conveyed over 
the joint to the movable part by means of a tendon. 
There are, however, a great diversity of arrangements 
in the smaller muscles, designed for the production 
of special and complicated motions. 

99. Bones as Levers. — To understand the mechanism 
of muscular motion, we must learn that bones are true 
levers, having the fulcrum, or fixed point of the lever, 
at the joint, the attachment of the tendon to the bone 
answering to what is called the power, and the extrem- 



MUSCLES. 75 

ity of the limb or part moved representing the weight. 
There may be three adjustments of these points in 
every lever, and all of these are found in the human 
body; but that which is commonly called the third 
form of the lever — that which places the power be- 
tween the fulcrum and the weight — is by far the most 
common arrangement. 

Fig. 45.— Muscular Motion. 



— , mm. ---MBjJI^S^^ 

n 

a. Flexor muscle of the arm. b. Tendon inserted into the radius. 
c. Extensor muscle, w. The resistance. 

100. Economy of Motion. — The general principle 
on which muscles are arranged is that of producing 
a great measure of motion by a very small amount 
of contraction. In Fig. 45, the muscle which is marked 
a is fastened by its tendon to the forearm at b. Now, 
if the muscle a is made shorter, it will draw b upward 
to the extent of its shortening; but an amount of 
motion at b will move the weight at iv as much further 
as the distance between iv and b. is greater than the 
space between b and the center of the joint. But this 
will require that the power applied at b be as much 
greater than the weight at iv as the space through 
which w is moved is greater than that through which b 
passes. This is the economy of motion at the expense 



76 



PHYSIOLOGY. 



Fig. 46. 
Movement in Walking. 



of power, and may be regarded as the general principle 
of muscular motion in the human body. 

101. Levers of the second and third classes. — In 

reversing the motion of the arm, as seen in the above 
cut (Fig. 45), the muscle c is attached by its tendon to 
a process of the ulna, which projects backward and 
upward beyond the joint, and the fulcrum is placed 
between the power and the weight. But the power 
being applied to the short end of the lever, produces, 

by a small motion there, a 
great motion at the weight 
end of the lever. 

In the foot we have the 
other adjustment, or second 
form of the lever, as seen in 
Fig. 46, where a is the large 
muscle on the back of the 
leg, which draws the heel 
upward when we rise on 
our toes ; b is the large bone 
of the leg, by which the 
weight of the body rests upon the bones of the ankle 
joint; c is the fulcrum or fixed point, on w T hich the 
whole weight of the body is raised in walking. 

102. The Power of Muscular Contraction.— It will 

be seen, from w T hat we have said, that the power 
exerted in the contraction of the muscles is many 
times greater than that manifested in the motions 
produced. This loss of power is not merely the effect 
of the application of the force to the short arm of 
the lever, but perhaps more is lost in power and 
gained in motion by the direction in which the force 




a. Large muscle of the leg- 
Tibia, c. The fulcrum. 



MUSCLES. 77 

is exerted. This is seldom in the line in which the 
motion is to be obtained, but usually very obliquely 
to it; as, for example, when a limb is to be bent, as 
the arm at the elbow joint, the muscles on the upper 
arm contract, but the tendency is chiefly to draw the 
bones of the fore-arm up against the humerus at the 
elbow joint. The tendency to bend the arm would be 
almost nothing if it were not for a contrivance by 
which the direction of the tendon, in passing over the 
joint, is changed. This is simply an enlargement of 
the humerus at its lower end, so that the tendon passes 
over it as over a pulley. 

103. Special Arrangements of Muscles. Number 
of Pairs. — There are many special contrivances for 
producing peculiar motions that are noticed and 
minutely described by anatomists, but which our pur- 
pose will not allow us to even name. The con- 
trivance by which the eyelids are closed in winking, 
and that which draws the low r er jaw downward in 
opening the mouth, are among the most curious and 
complicated of muscular movements. 

The muscles of voluntary motion are arranged in 
pairs on each side of the body, so that the right and 
left sides correspond exactly in the number and posi- 
tion of their muscles. Anatomists have named and de- 
scribed about two hundred and forty pairs of voluntary 
muscles, many of these, however, are very small, and 
apparently unimportant. 

Recapitulation. 

Bones are moved by muscles. These consist of fibers, and 
each fiber of cells. Muscular contraction is effected by chang- 
ing the form of cells. Tendons are used to attach muscles to 



78 PHYSIOLOGY. 

bones, and to transfer motion. Muscles are not generally situ- 
ated on the parts moved by their contraction. Bones are used 
as levers. Power moving them arranged to economize motion. 
Muscular contraction exerts a force greater than that realized 
through the mechanism of motion. Number of voluntary 
muscles — about two hundred and forty pairs. 



LESSON XIII. 

MUSCULAE MOTION — -VOICE. 

104. Muscular Motion — voluntary and involun- 
tary. — There is a number of very interesting phe- 
nomena connected with muscular action, two or three 
of which will be considered in this lesson. All animal 
motion, of whatever kind it may be, is produced by 
muscular contraction. A part of these motions are 
under the control of the will, and are therefore called 
voluntary motions; another class of motions are en- 
tirely independent of the will, or even the consciousness 
of the animal in which the motion is performed, and 
are called involuntary motions. 

The organs thus controlled belong more directly to 
the class on which depend the immediate functions 
of life. The heart and stomach are each active organs, 
but, in a healthy condition, we neither control nor 
feel their movements. The wisdom of this arrange- 
ment is very obvious, for it would be unsafe to trust 
such important functions to our voluntary attention. 

105. Articulate Language. — Thoughts, sensations, 
and emotions are communicated to others by mus- 
cular motion only. In man this communication is 
made chiefly by means of articulate language, and is 



THE VOICE. 



79 



much more extended and perfect than in the lower 
animals, whose Language consists of a few simple 
Bounds, accompanied by certain movements of the 
body which forcibly express a limited range of thought 
and passion. 

The barking of a dog, the purring of a cat, or the 
clucking of a hen, each, taken with the motions and 
attitudes of the body accompanying it, conveys mean- 
ing; but the thoughts, however forcibly they may 
impress us, are not communicated with the clearness 
of articulate language. The muscles of the human 
face, which, by contracting, change the features so as 
to give what is called expression 
to the countenance, greatly assist 
in making language impressive. 

106. Anatomy of the Larynx. — 

Voice is produced in an organ 
called the Larynx, which is placed 
on the top of the trachea. It con- 
sists of five cartilages, arranged so 
as to form a most perfect musical 
instrument, which, by means of 
air passed through it with more 
or less force, gives all the varied 
tones of the human voice. The 
Cricoid cartilage is a ring, narrow 
in front and broad behind, and is 
securely attached to the trachea 
by its lower margin. 
On the front part of this, and overlapping it, is placed 
the Thyroid cartilage; this is attached to a small 
U-shaped bone, situated at the root of the tongue, both 




d- 



"15 



"ii;ilK.v«j;rf 



a. Hyoicl bone. b. 
Thyroid cartilage. 

c. Cricoid cartilage. 

d. Trachea, e. Epi- 
glottis. 



80 



PHYSIOLOGY. 



Fig. 48.— The Glottis axd 
Vocal, Cords. 

6\ /b 



by a broad ligament and by muscles which move it 
in swallowing food, in speaking, singing, etc. The 
thyroid cartilage forms the projection on the front of 
the neck called Adam's Apple, by the motions of 
which the movements of the cartilage may be readily 
observed. 

107. Vocal Cords and Glottis. — Two small triangular 
bodies, called the Arytenoid cartilages, are placed on 

the back part of the cricoid 
cartilage, and so joined to it 
as to admit of considerable 
motion at the joint ; from these 
are stretched two pairs of liga- 
ments called Vocal cords, which 
are attached to the upper edge 
of the thyroid cartilage at the 
front part. The vocal cords 
are formed of very fine elastic 
fibers, inclosed in a delicate 
mucous membrane. The space 
between the upper and lower 
pair of cords is called the Ven- 
tricle, and the opening between 
the cords of each pair is called 
the glottis. These parts will 
be better seen in the figure attached. 




X^/^ 



\r 



a. Upper edge of the tnyroid 
cartilage, b, b. Arytenoid 
cartilages, c, c. Vocal cords. 
d. Glottis. 



108. The Epiglottis. — The Epiglottis is a thin, car- 
tilaginous valve, which closes the glottis by resting 
firmly on the upper pair of vocal cords, thus forming a 
kind of bridge, by which the food and drink are con- 
veyed safely over the glottis into the pharynx and 
oesophagus, which lie back of the air passage.. If we 



THE VOICE. 81 

attempt to speak or laugh while in the act of swallow- 
ing, the epiglottis will be raised, permitting the food 
or drink to fall into the trachea, and thereby produce 
strangling. 

In ordinary, quiet breathing, the vocal cords are 
relaxed, and the epiglottis thrown up, so as to partially 
close the passage into the mouth, and thus direct the 
air through the nasal passages. The upper pair of 
vocal cords serve chiefly as a resting place for the 
epiglottis, and are but little concerned otherwise in 
the ordinary production of voice. 

109. The Pitch of Yoice — its mechanism. — The 

lower cords are exceedingly delicate, and the edges, 
which form the glottis proper, are very fine, and w T hen 
drawn tensely, they present an instrument of vibration 
more perfect than any that has been produced by art. 
It is a well established principle, that the pitch of a 
sound, produced by a vibrating cord, is determined by 
its length, size, and tension. 

Now the vocal cords, fastened firmly at the back to 
the arytenoid cartilages, and running obliquely upward 
and forward, are attached to the front of the thyroid 
cartilage, and if this be drawn upward, it will make 
the vocal cords very tense. These, being elastic, dimin- 
ish in size as their tension increases. 

We have thus two conditions of elevated pitch, but 
we have by this movement lengthened the cords which 
would have a contrary effect. To counteract this, the 
arytenoid cartilages are drawn closer together, and as 
the cords are attached to the same point in front, if the 
back ends are brought closer together, the front part 
of the cords will touch each other, and thus virtually 
shorten the cord. 



82 PHYSIOLOGY. 

110. The Larynx as a wind instrument. — But the 

larynx is not merely a stringed instrument; perhaps 
it has more points in common with wind instruments. 
In these the notes are varied by the size of the aperture 
through which the air is forced into the tube, by the 
length of the tube, and by the velocity with which the 
air enters it. Now, as the thyroid cartilage is drawn 
upward, and the vocal cords are made tense and brought 
nearer to each other by the movement of the arytenoid 
cartilages, the glottis is diminished in size, while the 
tube (which consists of the mouth and nasal passages) 
is shortened by the amount that the thyroid cartilage 
is elevated. 

But when the organs of voice are placed in this con- 
dition, more force is required to expel the usual quan- 
tity of air from the lungs, and thus the last condition 
of a high pitch is secured. This explains why it is 
more fatiguing to speak or sing on a high key than on 
a lower one. 

111. Modulation of Articulate Sounds. — But the 

utterance of musical sounds, and the performance of 
most wonderful musical combinations, are not the most 
important or most difficult functions of the vocal ap- 
paratus. The rapid adjustment of the larynx, by the 
movements of a very complicated system of muscles, 
in the articulations of a rapid speaker, is one of the 
most marvelous of all the phenomena of the animal 
economy. 

While all vocal sounds are formed in the larynx, yet 
voice thus formed is modulated in the mouth and nasal 
passages. The organs concerned in modulation of voice 
are chiefh^ the lips, teeth, tongue, palate, and air pass- 



NERVOUS SYSTEM. 83 

ages of the nose. All have observed how the voice is 
affected by the loss of the front teeth, or by the imper- 
fect palate and lip in persons with harelip. The 
tongue, though important, is not the sole organ in 
modulating articulate sounds. 

Recapitulation. 

The larynx is the organ of voice. It is composed of five 
cartilages. Voice is produced by the vibration of the vocal 
cords. These are put in motion by air forced through the 
glottis from the trachea. 

The larynx has the properties of both a stringed and a wind 
instrument. Various means of modifying pitch, etc. Rapid 
movement of the vocal organs in speaking. Modulation of 
sound in the mouth and nasal passages. 



LESSON XIV, 



NERVOUS SYSTEM. 



112. Distribution of Vital Force, a brain func- 
tion. — The organs which we have described, with 
their functions, are simply the machinery of life. We 
have not yet looked into the engine-room from which 
the power is furnished to operate this wonderful ma- 
chinery, enabling it to perform the various functions 
of the living body. The instrument through which 
this power is distributed to every organ of the body, is 
the nervous system. 

This consists of the Spinal cord, Brain, and the 
nerves by which every organ is connected with these 
great centers of vital force. It has been customary to 



84 



PHYSIOLOGY. 



consider the brain as the primary organ, and the spinal 
cord and nerves as appendages to it; but we find, in 



Fig. 4!).— Front and back view of the Bkain 
and Spin at, Cord. 



a- 





a, a. Cerebellum, b, b. Cerebrum, c, c. Spinal cord. 
d. Medulla oblongata. 

the lowest class of vertebrate animals (the fishes), that 
the brain is very imperfectly developed, while the 
spinal cord, with its nerves distributed to all parts 
of the animal, is very perfectly formed. 

113. Cerebrospinal and Ganglionic Systems. — In- 
deed, we find in living bodies this ascending scale : 
in vegetables we have no trace of anything like a 
nervous system ; in the invertebrate forms of life, we 
find nerves distributed to the adjacent organs from local 
nervous centers, called ganglions, but no brain or spinal 
cord; in fishes, the brain is little more than an enlarge- 



NICUVOUS SYSTEM. 



85 



F i g. 50.— Bra rN— fro nt 

V I E W • 




a. Right hemisphere of the 
cerebrum. 6. Left hemi- 
sphere of the cerebrum. 

Fig. 51.— Brain— side 
view. 



ment of the forward end of the cord. As we ascend the 
scale of vertebrate life, however, we find the brain be- 
coming more and more promi- 
nent, till we reach the summit 
of perfection in man. 

The spinal cord and brain are 
generally regarded by anatomists 
as a single organ, which they 
call the Cerebro-spinal axis. 
The existence of this cerebro- 
spinal axis, in vertebrate ani- 
mals, does not supersede or dis- 
place the system of ganglions, 
as found in the lower types of 
animal life. This constitutes 
what is known as the Sympa- 
thetic system. 

114. The Two Hemispheres. c "" 

— The cerebro-spinal nervous 
system is symmetrical, being 
divided into right and left sides, 
corresponding exactly in num- 
ber, size, and position of the 
parts. In accordance with this 
arrangement, the brain is sep- 
arated, by a deep, vertical fissure, 
into the right and left hemi- 
spheres. This separation is not 
quite perfect, for, near the base 
of the brain, a broad band of 
fibers extends from one hemisphere to the other, thus 
forming a connection between them. 




a. Anterior lobe of the cere- 
brum, b. Inferior lobe. c. 
Posterior lobe. d. Cerebel- 
lum. 

Fig. 52.— Cerebellum- 
pack view. 




86 



PHYSIOLOGY. 



Transversely, the brain is divided into the Cerebrum 
or large brain, occupying the upper and front part 
of the skull, and the Cerebellum or small brain, sit- 
uated at the posterior base of the cranium. The spinal 
cord is divided longitudinally by a deep fissure, both 
on the front and back, leaving only a narrow bridge 
of the substance of the cord in its center. 



Fig. 53.— Bask of the Bkaix. 



*.... 



4 * 



115. Medulla Oblongata— membranes of the brain. — 

The spinal cord enters the cranium at the large open- 
ing in its base, called 
the Foramen Magnum, 
and extending upward 
and forward, forms a 
connection with the 
cerebellum backward, 
and with the cerebrum 
above. This portion 
of the spinal cord ly- 
ing within the skull 
is called the Medulla 
Oblongata. It is a 
kind of bulb, or en- 
largement of the up- 
per end of the cord, 
and consists of three pairs of bodies (Pyramidal, Resti- 
form, and Olivary), which are united pretty firmly 
together. 

Both the brain and spinal cord are securely wrapped 
in membranes. The outer one of these, the Dura Mater, 
is a dense, firm membrane, adhering strongly to the 
inner surface of the skull. The Pia Mater is a very 
delicate membrane, attached to the surface of the brain; 




a. Medulla oblongata, b. Pons varolii, 
c. Olfactory nerves, d. Optic nerves. 



NERVOUS SYSTEM. 87 

and as this surface is uneven, or convoluted, the Pia 
Mater dips down between these convolutions, separating 
them from each other. Between these membranes lies 
no, gauze-like coat, called the Arachnoid membrane. 
These serous membranes are subject to diseases both 
dangerous and difficult to cure. 

116. Gray and White Matter of the Brain. — The 

substance of which the brain is composed is very soft, and 
easily broken down in handling it. Being composed 
largely of albumen, it may be rendered quite firm by 
steeping it for some days in alcohol, after which it may 
be studied very satisfactorily. Like all other life-formed 
tissues, its ultimate form is the cell, or little globe. 
These cells, however, change their shape more rapidly 
in the brain than in any other tissue of the bod)'. 

The brain is not uniform throughout in its texture 
and appearance. In both the cerebrum and cerebellum, 
the central portion of the organ is nearly a clear white, 
and appears under the microscope to be fibrous in its 
texture. Surrounding this, and following the irregular- 
ities of the convolutions, we find a layer of gray or 
ash-colored matter, differing in thickness in different 
persons, but forming a marked feature of every brain. 
In the spinal cord, the relative position of these parts 
is inverted, the gray matter being in the center, and 
the white surrounding it. 

117. Gray and White Matter. — The proportion of 
gray matter to the white is greater in the cerebrum 
than in the cerebellum or spinal cord; and the nervous 
cords distributed from these to all parts of the body are 
made entirely of white matter, though the gray sub- 
stance appears again in the center of the ganglions, or 

B. P.— 8. 



PHYSIOLOGY. 



Fig. 54.— Transverse section of 
the Cerebrum. 



little brains attached to the sympathetic system. The 

gray matter consists of 
cells, often very irregular 
in their shape, and con- 
stantly changing form. 
The white part, while it 
appears to be made of 
fibers, is really composed 
of chains of cells, forming 
continuous tubuli, extend- 
ing from the gray part of 
the brain to the extremi- 
ties of the nerves. 

118. Cranial Nerves. — 

a, a. Gray matter of the brain. b,b. The nerves are COrds COm- 
White matter, c. Corpus callosum. poged Qf ft wMte gubgtance 

like that of the brain, extending to all the living tissues 

Fig. 55— Orjgix of the C rax tat, Nerves. 





a. Cerebrum, b. Cerebellum, c. Arbor vitse. d. Corpus callosum. e. 
Medulla oblongata. /. Olfactory nerve, g. Optic nerve, h. Trifacial 
nerve, i. Auditory nerve. 

of the body, and connecting all the organs with the gray 



NERVOUS SYSTEM. 



89 



Fig. 56. — Origin of the Spinal 

Nfrves. 



matter of the brain or spinal cord. These nerves are 
arranged in pairs, corresponding to cadi other on the 
different sides of the body. Twelve pairs of these come 
off within the skull, and are sent to the different organs 
on which they are distributed through openings in the 
bones. These are called Cranial nerves. 

The first and second pairs, being the Olfactory and 
Optic nerves, appear to come off from the lower part 
of the front lobe of the cerebrum, but their principal 
fibers have been traced backward to the upper part 
of the medulla oblongata. The fifth pair, immediately 
after passing out of the 
skull, divides into three 
branches. From this fact 
it is sometimes described 
as three nerves. The 
ninth and tenth pairs, 
as they leave the skull 
through the same open- 
ing, have been described 
as one pair by some anat- 
omists. 

119. Spinal Nerves.— 
The spinal cord gives 
origin to thirty-one pairs 
of nerves, eight of which 
come off from the spinal 
cord in the neck, and are 
called Cervical nerves ; 
twelve in the back, which 
are named Dorsal nerves ; five from the loins, which are 
known as Lumbar nerves; and six pairs come from 




a, a. Brachial plexus, 
plexus. 



b, b. Lumbar 



90 PHYSIOLOGY. 

the termination of the cord in the sacrum, and are called 
Sacral nerves. The four lower cervical and the upper 
dorsal nerves on each side unite with each other, and 
separate again to be distributed on the upper extremity. 
This is called the Brachial Plexus. The last dorsal 
and the five lumbar nerves form a similar combina- 
tion, called the Lumbar Plexus. 

Recapitulation. 

The nervous system is the distributer of vital force. It con- 
sists of spinal cord, brain, and nerves. The nervous system is 
symmetrical, being divided into right and left sides. 

The two hemispheres are connected by the corpus callosum. 
The brain consists of cerebrum, cerebellum, and medulla ob- 
longata. 

The brain consists of an outer gray substance made of cells, 
and an inner white matter composed of fibers, or tubuli. 

The nerves connect all the organs with the brain and spinal 
cord. 



LESSON XV. 

NERVOUS SYSTEM. — CONTINUED. 

120. Complex Function of the Brain. — The organs 

comprising the systems of nutrition and voluntary 
motion have, as a general rule, but a single function 
each; but in the nervous system this rule is violated. 
The spinal cord and brain, considered as a single organ, 
performs at least three distinct and independent func- 
tions : 1st. it is the source, either directly or indirectly, 
of all muscular motion ; 2d. it is the seat of sensation ; 
and, 3d. it is the organ of thought. 



NERVOUS SYSTEM. 91 

These several functions, if not absolutely independent 
of each other, are so in a degree that is truly wonderful. 
The intellectual powers may be deranged so as to pro- 
duce a true insanity, with scarcely any disturbance 
of the functions of motion or sensation. On the other 
hand, in paralysis there may be entire loss of motion or 
sensation in many of the organs, while the mental 
activity remains unimpaired. 

121. Nerves of Special Sense. — The functions of 
motion and sensation are carried on by the brain exclu- 
sively through the agency of nerves, but the connection 
of the brain with the intellectual phenomena appears to 
have no direct association with the nerves. 

The first,* second, and eighth pairs of nerves are de- 
voted exclusively to special sensations. The first pair 
are appropriated to the sense of smell, and are therefore 
called the Olfactory nerves. They are distributed on 
the mucous membrane of the nasal cavities. The sec- 
ond pair are the Optic nerves, which furnish the eye 
with the power of vision. The nerves of hearing are 
the eighth pair. They are distributed on the internal 
ear, and are the only cranial nerves that do not pass 
out of the skull. The sense of taste is the function of a 
branch of the fifth and eighth pair of nerves on each side. 

122. Motor and Sentient Nerves. — The nervous 
trunks which perform the mixed functions of sensation 
and motion originate by two separate roots, each de- 
voted to its appropriate office. This is more distinctly 
seen in the spinal nerves, where, at each joint of the 
spinal column, nerves pass out, right and left, from the 
spinal cord. These have each an anterior and a pos- 
terior root, the first originating from the front, and the 



92 



PHYSIOLOGY. 



Fig. 57.— Motor and Sen 

tient Roots of the 

Spinal Nerve. 



a. 



,b 



jJmt IS 




a, a. Anterior or motor 
root. 6, b. Sentient or 



last from the back part of the spinal cord. If the an- 
terior root be injured or diseased, the power of motion 

is lost or impaired in the parts 
to which the nerve is distributed; 
but if the injury is in the poste- 
rior root, the power of sensation, 
or feeling, is impaired in the 
parts supplied by that nerve. 
The anterior is therefore called 
the Motor root, and the posterior 
the Sentient. 

123. Distribution of Nerves. 

— The sentient root is slightly 
larger than the motor, and has 
posterior root with its a ganglion or enlargement on it 

ganglion exposed by re- bf it . {m ^ g^ 

moving the motor root. J J 

This union takes place before 
the nerve passes through the opening between the 
vertebrae, and beyond this the nervous cord appears 
to consist of but one kind of fibers or tubuli, but at the 
termination of the nervous branches the distinction of 
function is again observed. 

The nervous trunks, by sending off branches, dis- 
tribute themselves over the parts they are intended to 
supply. In this distribution, though the branches of 
nerves are sent to almost every organ of the body, yet 
the supply furnished to different organs is not by any 
means the same. 

124. Motor and Sentient Nerves terminate differ- 
ently. — The nerves of motion and those of sensation 
differ most widely in their functions, yet the most 
careful examination with the best microscope fails to 



NERVOUS SYSTEM. 93 

reveal any difference in their structure so long as the 
fibers remain wrapped in the same nervous envelope; 

but as we trace the nervous trunks toward their ex- 
tremities, the filaments of different functions separate 
from each other, and in their terminations there is a 
very marked difference in their appearance. The nerves 
of motion continue to divide, until their filaments be- 
come so fine that even the microscope scarcely enables 
us to trace them. They are distributed entirely to the 
muscular system, and terminate on the ultimate cells 
composing the muscular fibers, and communicate to 
them the power by which the fiber is shortened, and, 
consequently, the whole muscle contracted. 



125. Pacinian Corpuscles. — The nerves of sensation, 
as they approach their extremities, are usually folded 
back on themselves, so as to form a kind of loop; and 
sometimes this folding is repeated two or three times, 
so as to produce a distinct enlargement at the end of 
the nervous filament. This repeated folding of the 
nervous tubuli forms what are called Pacinian corpus- 
cles. They are found in the nerves terminating on the 
hand and foot more frequently than in any other part 
of the body. They appear to be connected with the 
special sense of touch, as they are found in the upper 
lip of the horse, and in the end of the elephant's trunk. 
Some have supposed them to be organs for producing 
animal electricity, as they resemble somewhat the 
organs of certain electric fishes. 

126. Sentient Nerves on the Skin. — But the single 
loop, or simple folding back on themselves, is a mode 
of termination common to all sentient nerves, whether 
the sensation is merely feeling, or is some special form 



94 



PHYSIOLOGY. 



of sensation, as seeing, hearing, tasting, or smelling. 
The surface of the skin is so well furnished with 
sentient nerves, that it is impossible to put down the 
point of a needle anywhere on it without touching one 
of those loops terminating a nervous filament, and 
thus communicating to the brain intelligence of the 

Fig. 58.— Nerves of Sensation, with their Terminal Loops 
greatly magnified. 




injury. B} r this arrangement, every part of the body 
that is liable to be injured by foreign substances, is 
kept in constant communication with the brain, where 
consciousness resides, and from whence proceed all 
voluntary motions. 

127. Mystery of Sensation. — This power of feeling 
is a wonderful endowment. An impression is made on 
a looped extremity of a sentient nerve, in some remote 
part of the body. Instantly, the filament of nerve 
thus impressed communicates the impression along 
the nervous cord, where this particular filament is 
entangled and interlaced with a thousand similar ones ; 
and yet the impression is not communicated to them, 
but is confined to the individual filament; it passes 
through the interior white matter of the brain, and 
finally reaches the gray substance, where perception 
or consciousness appears to reside. This perception 
not only locates the precise spot where the impression 



NERVOUS SYSTEM. 95 

was made, but also determines the nature of the im- 
pression, and, within certain limits, the character of 
the substance or agent making it. 

128. Injury of a Nervous Trunk. — The office of the 
nerves is illustrated in the phenomenon of a paralyzed 
limb. If the great nervous trunks, returning to the 
brain the impressions made on any particular part 
of the body, be destroyed, the person has no knowledge 
of the condition of that part; but if the injury be 
partial or temporary, the perception will be impaired 
or confused as to the place of the impression or its 
nature. Thus, by an improper attitude, we sometimes 
compress the nervous trunk conveying impressions 
from the hand or foot, and a peculiar, prickling sen- 
sation is felt in the part on which the nerve ter- 
minates. This is expressed in common language by 
saying that the hand or foot " is asleep." 

Recapitulation. 

The nervous system performs the functions of motion, sensa- 
tion, and thought. Nerves devoted to sensation alone, have but 
a single origin; nerves of both sensation and motion, originate 
by two roots. Nerves of sensation terminate in loops; those of 
motion by filaments distributed on the muscles. Between their 
origin and termination the nervous trunks are alike. When 
impressions are made on the trunk of a sentient nerve, the 
sensation is referred to the extremity. 
B. P.— 9. 



96 PHYSIOLOGY. 



LESSON XVI. 



SENSATION. 



129. Low Sensibility of Bone, Cartilage, etc. — The 
power of sensation is not distributed alike to all the 
organs of the body. The bones and cartilages have no 
feeling when in a healthy condition; but when they 
are inflamed, they become highly sensitive. This is 
probably owing to some peculiar condition of the 
nerves in the solid substance of these tissues, which 
is not well understood. 

The fatty deposits, which often accumulate to a con- 
siderable thickness between the skin and muscles, as 
well as in other parts of the body, are nearly destitute 
of feeling, having but few nerves distributed on them. 
The muscles which produce the voluntary motions of 
the body, while they are the only points of distribution 
for the motor nerves, are but moderately supplied with 
nerves of sensation ; and consequently the muscles, when 
in a healthy condition, have but little feeling. The 
organs of involuntary motion, such as the heart, etc., 
are entirely insensible, except in a diseased state. 

130. Sense of Touch in the Fingers. — The skin, 
and the mucous membrane lining the mouth and 
glottis, are the chief seats of sensation. The skin, on 
different parts of the body, has different degrees of 
sensibility. The fingers and toes have the largest num- 
ber of sentient nerves distributed on their surfaces, and, 
consequently, have the most acute sensibility of any 
of the organs of the body. Indeed, the surface of the 



SENSATION. 97 

true skin on the ends of the fingers appears to be made 
up of bundles of sentient nerves, or their loop-like 
terminations, forming those little elevations, called the 
papillae, which cover these parts. So highly endowed 
with sensibility arc these organs, that some have re- 
garded them as special instruments of a local sense, 
differing from the general sensibility of the body; but 
the function appears to differ in degree, rather than in 
kind. 

131. The Grades of Sensation — Muscular Sense.— 

A careful analysis of this subject will reveal at least 
three distinct grades of sensibility, located in different 
organs of the body ; and, in some of them, the sensation 
varies in acuteness in different parts of the organ or 
organs to which the sensation is referred. First in the 
group of sensations, and lowest in the distinctness of its 
impressions on the perceptive powers, is the subjective 
or internal sense, sometimes called the muscular sense. 
The most obscure manifestation of this is in those sen- 
sations which we call weariness, fatigue, faintness, etc. 
These sensations appear to be rather general than 
special, and therefore can hardly be referred to any 
particular locality in the body. 

The sensation of weight, or resistance to muscular 
action, is a little better defined, but still very difficult 
to locate. If we extend the hand, and place a piece 
of card-paper on the fingers, we will perceive merely 
the sensation of touch ; but if a two-pound weight be 
substituted for the card, a very different sensation is 
felt — a perception of what we call weight. 

132. Sense of Touch, of Taste and Smell. — A 

second class comprises those sensations which are made 



98 PHYSIOLOGY. 

by contact with external objects, and referred definitely 
to the point of contact, and also where the perception 
determines something in relation to the character of the 
body producing the sensation. 

For example, the sense of touch determines where 
the person is touched, and whether the substance pro- 
ducing the sensation is rough or smooth, hard or soft, 
hot or cold, etc. But the tongue not only conveys to 
the brain the sensation of being touched, and the usual 
knowledge of the physical properties of the body touch- 
ing it, but also a peculiar sensation which is called 
taste. It is a special sensation, and is definitely re- 
ferred to the mouth. So, also, the olfactory nerves convey 
to the brain the sensation produced by odorous bodies. 

133. Organs of the Sense of Smelling. — This second 
group of sensorial functions ascends, in point of delicacy, 
from the mere sense of contact common to the whole 
surface of the body, to the sense of smell, which recog- 
nizes odors so exceedingly delicate that no other test 
can detect their presence. This sense has a pair of 
nerves especially appropriated to it; and though the 
sentient extremities of these nerves are distributed on 
the mucous membrane of the nasal passages, which 
differs nothing in appearance from the mucous mem- 
brane forming the surface of other open cavities, yet 
the delicacy of the olfactory sense falls but little below- 
that of senses of the third class, each of which has 
a special apparatus appropriated to its use. In some 
of the lower animals, such as the dog and the vulture, 
this sense is much more acute than in man. Many 
animals which live in the water have the sense of 
smell greatly developed. 



SENSATION. 99 

13+. Use of the Turbinated Bones. — The nasal 
cavities have their surfaces greatly extended by the 
turbinated hones. These are thin plates of bone, rolled 
up and placed, one in each nasal chamber, and covered 
throughout with the membrane, on which the olfactory 
nerves are distributed. 

These air passages are so placed that the air, in 
ordinary breathing, scarcely enters them ; but when a 
voluntary effort is made to exercise the function of 
smelling, it is drawn forcibly through the passages, and 
made to enter the cavities among the folds of the 
turbinated bones, and thus greatly to increase the 
surface in contact with the odors inhaled. There 
appears to be a strange complication of the sense of 
smell with that of taste, so that much of what is usually 
regarded as taste really belongs to the olfactory sense. 

135. Simple Nature of the Olfactory Sense. — The 
sense of smell appears to be the least complicated of all 
our sensations. When we place our hand on the table, 
we have, first, a sense of contact with something exter- 
nal to ourselves; then, in quick succession, the sensa- 
tions which determine hardness, smoothness, tempera- 
ture, etc., each one of which appears to be the exercise 
of a special function, but all taken together form the 
Pcomplex sensation which we call feeling. On the other 
j hand, if we inhale a powerful odor, such as musk, for 
example, we have no distinct sensation of contact, no 
clear perception of any thing outside of ourselves, no 
indication of the direction from which the odor came, 
no ideas of size or shape are derived from the sensation ; 
all we acquire is a knowledge of that indefined property 
called odor. 



100 PHYSIOLOGY. 

A singular fact about the exercise of this sense is 
that, while we distinguish odors, and identify them as 
the property of certain substances, yet we have no 
names for odors, but describe them only by com- 
parison. 

136. Ability to suffer Pain, important to our 
Safety, — These lower grades of sensation are of the 
utmost importance to the safety and enjoyment of the 
individual. The senses of taste and smell are the chief 
guides on which we rely in the selection of our food; 
and the sense of feeling, which rises to pain when the 
contact is violent, continually admonishes us of danger 
from surrounding objects. Our safety depends more on 
our ability to suffer pain than most persons apprehend. 
Those who, from disease or accident, have lost the sense 
of feeling in a limb, often sustain serious injury, from 
burns or other accidents, before they are aware of 
danger. These senses may therefore be regarded as 
body-guards or sentinels, placed on the outposts of the 
citadel of life to give timely warning of the approach 
of friend or foe. 

Recapitulation. 

Sensation is unequally distributed among the organs. Sense 
of feeling is distributed over the surface of the body generally. 
Special sense of touch located in the ends of the fingers. 
Three grades of sensations: 1st, muscular sense; 2d, touch, 
taste, and smelling; 3d, seeing and hearing. Olfactory sense 
located in the nasal passages. Peculiar arrangement of the 
turbinated bones. Smelling the least complicated of all the 
senses. 



THE EAR. 101 



LESSON XVII. 

ORGANS OF SPECIAL SENSE. 

137. Senses which have Special Organs. — The third 
and highest class of sentient functions have each a 
special apparatus appropriated to them, by means of 
which they make us acquainted with properties and 
conditions of bodies around us, that are entirely be- 
yond the reach of ordinary sensation. The special 
senses of hearing and seeing form this class. 

The Ear, the organ of hearing, consists of the external 
ear, the tympanum or middle ear, and the labyrinth or 
internal ear. The external ear consists of a tube about 
an inch in length, which in man and in most mam- 
mals spreads out into a broad expansion externally. 
Both the tube and the expanded rim are formed of a 
firm, elastic cartilage. In birds and reptiles the exter- 
nal expansion is wanting; and, in fishes, the rudiments 
of the internal ear are found, but no vestige of an outer 
ear has been discovered. 

138. The External Ear. — In the human subject, 
the external expansion forms an irregular, semicircular 
plate, concave on its forward and outer surface, and cor- 
respondingly convex on the opposite side. Its purpose 
is to collect and concentrate the vibrations of the air at 
a central point, which is the external opening of the 
auditory tube. 

This opening is protected from the intrusion of dust, 
insects, etc., by a cluster of stiff, short hairs placed near 
the entrance ; but a more effectual protection is afforded 



102 



PHYSIOLOGY. 



by a yellow, tenacious, bitter wax, secreted by a number 
of small glands on the inner surface of the auditory 
tube. Across the bottom of this tube is drawn a fine 
membrane, so as to close it completely, and thus cut 
off all communication with the middle ear. 



139. Drum of the Ear— Eustachian Tube. — The 
Tympanum, or drum of the ear, is a cavity in the 
hard portion of the temporal bone. While it is cut 
off from direct communication with the external air 
by the drum-head, or membrane of the tympanum, just 
now described, that communication is indirectly estab- 

FiG.59-TiiEEAn. lished through the 

posterior chamber of 
the mouth, by means 
of a funnel-shaped 
canal, called the Eu- 
stachian tube. The 
narrow end of this 
tube passes through 
a small opening, or 
foramen, into the 
cavity of the middle 
ear, while the broad 
end establishes a 
communication with 
the upper portion of 
the pharynx, and by 
this means the tympanum is kept filled with air. In 
yawning, the Eustachian tube is compressed, and some- 
times the sides temporarily adhere together, occasioning 
an unpleasant roaring in the head, till, w T ith a crackling 
sound, the obstruction is removed, and all is right again. 




a. External ear. b. Auditory tube. c. Tym- 
panum, or middle ear. d. Semicircular 
canals, e. Vestibule. /. Cochlea, g. Eu- 
stachian tube. 



THE EAE. 



103 



Fig. GO.— Bonks of the Middle 
Ear, enlakgkd. 




140. Hones of the Ear.— In the cavity of the tym- 
panum there arc lour small bones, articulated together 
so as to form a bony 
chain, stretching from the 
tympanic membrane to 
the membrane closing the 
aperature communicating 
with the inner ear. These 
bones are named, from 
their fancied resemblance 
to the objects, the malleus, 
or hammer; the incus, or 
anvil; the orbiculare, or 
round-bone ; and the stapes, 

or stirrup. The handle of the hammer is fastened to 
the middle of the drum-head, while the head of the 
hammer fits into the cavity of the anvil, and the horn 
of the anvil is attached, by means of the round-bone, to 
the bow of the stirrup, the base of which rests firmly 
against the membrane closing the passage into the 
labyrinth. 



a. Malleus, or the hammer, b. In- 
cus, or the anvil, c. Orbiculare, or 
the round-bone. d. Stapes, or the 
stirrup. 



141. Injuries of the Middle Ear — their effect. — 

This chain of bones is furnished with very delicate 
muscles, which serve to render it tense, so that the 
slightest vibration is transmitted along it from the 
outer to the inner ear. These bones are sometimes 
destroyed by disease or accident, without the entire 
loss of hearing, though always with great injury to 
that function. 

The dullness of hearing common to old age is usually 
the result of the growing together of this bony chain, 
as well as of the thickening of the membranes at each 



104 



PHYSIOLOGY. 



end of the chain. These changes are often accompanied 
by the more or less complete closure of the Eustachian 
tubes. While perfect deafness seldom results from inju- 
ries to the middle ear, yet most of the causes which 
operate to merely impair hearing are located there. 

142. The Labyrinth, or Internal Ear. — The Laby- 
rinth is composed of three parts : the vestibule, the 
semicircular canals, and the cochlea, or snail-shell. The 
vestibule is a common chamber with which all the 
other parts communicate. It is a small, oblong, irregu- 
larly shaped cavity in the hard portion of the tem- 
poral bone, with two small openings looking into the 
middle ear. These are called finestrze, or windows, and 
from their respective shapes are named the oval and 
the round windows. These, in the living body, are 
closed by a dense, firm membrane, but, in the skeleton, 
appear as openings from one chamber to the other. 

143. The Semicircular Canals— their use. — Some 

idea of the form and 
fig. 61,-the Internal ear. relation of the several 

parts of the inner ear 
may be obtained from 
the annexed figure, 
which represents the 
internal ear, somewhat 
enlarged. 

The semicircular ca- 
nals, three in number, 
are simply curved 
openings through the 
bony substance sur- 
rounding this cavity, passing out of the vestibule and 




a. Vestibule, b. Cochlea, c. Semicircu 
lar canals, d. The oval window, e 
The round window. 



THE EAR. 105 

returning to it. If they serve any other purpose than 
to extend the surface for the distribution of the auditory 
nerve, th^t purpose has not been discovered. 

144. The Cochlea. — The Cochlea, or snail-shell, is a 
double spiral canal, wound around a central pillar. 
Leaving the vestibule opposite to the oval window, it 
makes two and a half turns around the pillar and 
reaches the summit, where it enters the other canal, 
and by the same number of turns as in ascending, it 
descends to the vestibule, reaching it at the round 
window. All these cavities are filled with a limpid 
fluid, which is nearly pure water; and they are lined 
by a very delicate membranous expansion of the audi- 
tory nerve. In the vestibule and semicircular canals, 
this nervous expansion is covered with filaments, or 
loops of nerve matter, floating loosely at one extremity, 
and attached to the nervous mass by the other. In the 
cochlea, the nervous expansion presents a smooth, soft 
surface. 

Recapitulation. 

Seeing and hearing are senses with special organs devoted to 
them. The ear consists of the external, middle, and internal 
divisions. The middle ear communicates with the mouth by 
the Eustachian tube. It contains a chain of four small bones. 
Its cavity is filled with air. The internal ear consists of a 
vestibule, a cochlea, and three semicircular canals. These 
cavities are filled with water. The auditory nerve is distributed 
on the membrane. 



106 PHYSIOLOGY. 



LESSON XVIII. 



HEARING. 



145. Nature of Sound, — The complex organ which 
we attempted to describe in the last lesson, is intended 
to convey to the brain the sensation of sound, and its 
several properties and qualities. The sense of hearing 
takes cognizance of a tremulous or vibratory motion 
transmitted through a medium (usually the air) from a 
vibrating body, to the auditory nerve in the inner 
ear. 

All bodies are not capable of emitting sound. Elas- 
ticity and hardness are the properties which are com- 
monly assigned to sonorous bodies, but this definition 
appears to be defective. Two currents of air striking 
each other will give out sound, without the assistance 
of any hard substance. Elasticity is an indispens- 
able property of sonorous bodies, and yet but few sub- 
stances are more elastic than India rubber, and none 
less sonorous. 

146. Transmission of Sound-waves. — A bell is struck 
with a hammer, and instantly the particles of which it 
is composed are thrown into a kind of wave-like motion, 
which is prolonged for several seconds. This vibration 
can be easily perceived if we bring our fingers into 
contact with the bell immediately after the stroke. 
This movement is transmitted to the surrounding air, 
and waves of motion, exactly corresponding to the 
vibrations in the bell, roll off in every direction, di- 
minishing, however, in intensity as they recede from 



HEARING. 107 

the sonorous body, but retaining all the other properties 
of the original vibration in the bell. 

Air is not the only medium of communication 
between sounding bodies and the organ of hearing. 
Dense solids, such as the metals, compact wood, etc., 
are good conductors of sound, and water transmits 
sonorous vibrations very perfectly. 

147. Conditions of the Transmission of Sound.— 

Sound is not transmitted through a vacuum, hence a 
bell struck in the exhausted receiver of an air-j)ump 
gives out no sound, because there is nothing in contact 
with it to communicate its vibrations to the outer air. 
Sound is transferred with difficulty from one medium 
to another. A bell struck under water gives scarcely 
any sound to the ear in the air, but if the ear be under 
water, the sound is almost deafening. 

Though wood is an excellent conductor of sound, yet 
a wooden partition of but an inch in thickness greatly 
interrupts the passage of sounds. This is because the 
vibrations have to be transferred to the wood from the 
air, and after passing the wood, re-transferred to the air 
again, by which a large proportion of the original in- 
tensity is lost. Air contained in a tube transmits sound 
much more perfectly than when unconfined, because the 
vibrations are not readily communicated to the sur- 
rounding walls of the tube. 

148. Reflected Sound. — Waves of sound, transmitted 
through the air, striking on a solid surface, communi- 
cate but a small amount of their motion to the ob- 
structing solid. The greater portion is reflected or 
turned back again into the same medium. This re- 
flected wave of sound forms what is called the echo, 



108 PHYSIOLOGY. 

and is always less intense than the original sound, by 
the amount of vibration communicated to the reflecting 
surface. Obeying the law of reflection, sound may be 
concentrated by being reflected from concave surfaces, 
and diffused when thrown off from convex ones. On 
this principle ear-trumpets act, to collect at a single 
point the sonorous vibrations of a large space. The 
cartilaginous expansion of the outer ear serves the 
same purpose. 

149. Mechanism of Hearing. — The undulations, or 
waves of sound, thus concentrated by the expansion 
of the external ear, strike on the tense membrane of 
the tympanum at the bottom of the auditory tube, 
communicating to it similar vibrations. But as one 
end of the chain of bones in the middle ear is attached 
to the tympanic membrane, whatever state of motion is 
induced in it will be transmitted along the bony con- 
nections to the stirrup, the base of which presses firmly 
against the membrane of the oval window. 

The arrangement of these bones is such as to slightly 
magnify the movement, and to limit it to a single 
direction. The stirrup-bone moves to and from the 
membrane with which it is in contact, and can have 
no lateral or side motion. But the inner ear, in all its 
parts, being filled with fluid, has the vibration of the 
membrane communicated to it throughout, by the well- 
known law of the transmission of impressions through 
fluids. 

150. The Qualities of Sound. — The expansion of 
the auditory nerve being every-where in contact with 
this fluid, and its sentient loops floating loosely in it, 
transmits to the brain the intelligence of the vibration. 



HEARING. 109 

The sensation thus conveyed to the seat of perception 
is an exceedingly complex one, embracing, beside the 
simple impression of sound, the almost innumerable 
qualities and modifications of it. 

The chief of these may be comprised in the intensity 
or force, the pitch, and the direction of sound. The 
force or loudness of a sound is often mistaken for its 
pitch, because a sound on a high key produces the 
jarring sensation of a much louder sound on a lower 
key. The length of the undulations, or what is the 
same thing, the number of vibrations in a given time, 
constitutes the pitch of a sound, without any reference 
to the force by which the vibration is set in motion. 

151. The Direction of Sound, how determined.— 

The power to determine the direction from w T hich a 
vibration proceeds, is not the least of the wonders of 
this wonderful sense. If we were to reason from the 
mechanical arrangement of the ear, we would infer that 
all sounds, when communicated to the auditory nerve 
through the tube of the external ear, the chain of bones 
in the middle ear, and the fluid of the labyrinth, would 
be converted into waves in a uniform direction; but 
this is not the case. As the wave of sound rolls 
out in every direction from the vibrating body, it is 
evident that a line drawn from that body must cut the 
wave at right-angles, at whatever point it may strike it. 
That which the auditory sense determines, therefore, is 
the direction of a line that shall be at right-angles with 
the undulations. In a practiced ear, this delicate task 
is performed with amazing accuracy. 

152. Musical Faculties. — But the nice discrimina- 
tions of a well disciplined musical ear, are even more 



110 PHYSIOLOGY. 

wonderful than the measurement of the angle necessary 
to determine the direction of sound. This is a special 
faculty, and does not depend alone on the acuteness of 
hearing. Many persons who hear accurately even very 
feeble sounds, and judge correctly of their other prop- 
erties, yet distinguish the pitch of sounds very im- 
perfectly. Many eminent physiologists have referred 
this faculty to the cochlea or spiral canals, and there 
appears to be plausible reasons for such reference. 
However, in the present state of anatomical knowledge, 
it would be hazardous to affirm any thing on the subject. 
The power to distinguish the voice of a particular 
person, is really as strange as the most wonderful 
musical powers. 

153. The Sense of Hearing — how far it is vol- 
untary. — The sense of hearing is properly an invol- 
untary function, though there are several modifications, 
subject to the will, which have an important bearing 
on the exercise of this faculty. For example, if the 
attention be directed to a certain sound, we can, by a 
voluntary effort, transmit that sound to the perceptive 
center, and practically exclude all others, though they 
may be more forcible. 

There is also a voluntary power of increasing the 
tension of the tympanic membrane, thus rendering the 
ear more sensitive, and capable of hearing very feeble 
sounds. The sense of hearing can be educated, in its 
several departments, to an almost unlimited extent, 
as is witnessed in the trained musician, and the 
telegraph operator. 

The organs essential to hearing being located in a 
bony cavity, are subject to fewer accidents than most 



THE EYE. Ill 

of the other organs; but a long continued exposure to 
loud and constant noises, as in machine-shops and 

factories, greatly impairs the acuteness of hearing. 

Recapitulation. 

The ear acquaints us with sound and its qualities. Hard, 
elastic bodies, when vibrating, communicate their motion to the 
air, or other medium with which they are in contact. This 
vibration is transmitted to the inner ear through the drum by 
means of the bony chain, and a similar motion is set up in the 
fluid of the internal ear. The auditory nerve transmits to the 
brain the knowledge of this vibration. The brain recognizes 
the sound — its force, pitch, direction, etc. Hearing is involun- 
tary, but may be modified by volition. 



LESSON XIX. 

THE EYE. 

154. Muscles of the Eye. — The Eye, the organ of 

vision, consists of the globe or ball of the eye, the 

adjusting machinery, and the protecting organs. The 

two last-named divisions, however, are merely auxiliary 

organs, and not absolutely essential to vision. The 

adjusting machinery consists of six muscles, w\hich 

arise from the back part of the bony socket in which 

the ball of the eye is placed. Four of these are called 

straight muscles. They are inserted into the back part 

of the orbit, about equal distances apart, so that while 

two serve to roll the eye upw T ard and dow T mvard, the 

other tw r o give it a lateral motion to the right and 

left. 

B. P.— 10. 



112 



PHYSIOLOGY. 



The remaining two are called oblique muscles. They 
are inserted into the outside of the eyeball, and operate 
to roll it inward and downward. One of these has a 
peculiar contrivance for this purpose. It arises with 
the straight muscles from the back of the orbit, but is 

Fig. 62.— Muscles of the Eye. 




a. Globe of the eye. b, b, b. Straight muscles, c. Muscle to raise 
the upper eyelid (Levator Palpebrce). d. Upper oblique muscle. 
e. Loop and tendon. 

carried forward and upward by a slender tendon, which 
passes through a loop of firm ligament attached to the 
upper and inner margin of the bony socket of the eye, 
from whence, turning back, it is inserted into the outer 
and back part of the ball. 

155. Arrangements for Protecting the Eye. — The 

protecting organs are several, and, taken together, con- 
stitute a very perfect system of protection to a very 
delicate organ, whose function requires that it shall 
have a large external exposure. The ball of the eye, 
the true organ of vision, is placed in a deep, bony 
socket, the margin of which is guarded above by a 
heavy ridge of bone in the form of an arch. The eye- 
ball, in this cavity, rests on a soft, elastic cushion of 



THE EYE. 



113 



fatty matter, which entirely fills the back part of the 
socket. 

The eyelids are a pair of curtains, with each a thick, 
cartilaginous edge fitting accurately to its mate, and 
thus completely excluding the eye from the outer world. 
These margins are lined with short, curved hairs, the 
eyelashes, which serve as a screen to protect the eye 
from dust. The bony ridge above the eye is also cov- 
ered with a line of short, thick hairs, inclining toward 
the outer angle of the eye, so as to carry the perspira- 
tion around that organ. 

156. Tears — their use — the Lachrymal Duct, — 

That it may perform its function properly, the eye 



P'IG. ftl-LACHKYMAL GLAND AND DUCT. 



,a 




d— 



a. Lachrymal gland, b. Ducts leading from the gland to the 
upper part of the eye. c, c. The lachrymal points, d. Nasal 
duct. 

requires to be kept constantly moist. To accomplish 
this end, a gland, called the Lachrymal gland, is placed 
in a depression of the orbit immediately back of the 
arch, at its upper and outer part. This gland secretes 
the fluid called tears, and, from its situation, this secre- 



114 



PHYSIOLOGY. 



tion is very readily distributed over the front part of 
the ball, by the motion of the eyelids in winking. 

The inner surface of the eyelid is covered with a 
very delicate and highly sensitive membrane, called 
the conjunctiva. This is reflected off from the eyelid 
to the ball, and covers the front part of it, one layer 
of it passing entirely over the transparent cornea in 
front of the eye. The tears, after having performed 
their office, are conveyed into the nose by the lach- 
rymal duct, which opens into the orbital cavity near 
the inner angle of the eye. 



157. Coats of the Eye. — The ball of the eye is a 

complete optical instrument, a camera of the same 
kind used by artists in making sun-pictures, but in- 
finitely more perfect 
fig. &4.-THE eye. than any instrument 

which human ingen- 
uity and skill has yet 
produced. The eye has 
three distinct coats. 
The outer one of these, 
called the Sclerotic 
coat, is a dense, tough 
membrane, approach- 
ing nearly to the firm- 

a. The three coats of the eye. b. The ness Of Cartilage, 

cornea, c. The aqueous humor, d. Oil the front part 

The crystalline lens. e. The vitreous * ,, , ,, ' ,, . , 

humor. /. Optic nerve. ° f the h f l > tlllS COat 

changes its character, 
becomes transparent and slightly thinner, but preserves 
its hardness. This transparent portion is called the 
Cornea. It is more convex than the sclerotic coat 



&'' 




THE EYE 



115 



Fig. 65.— Ikis, Pupil, and 
Ciliary Processes. 



elsewhere, as if it were a segment cut from a smaller 
Bphere. The Choroid coat is a highly vascular mem- 
brane, lying in immediate contact with the inner sur- 
face of the sclerotic coat. It contains numerous cells 
filled with a dark brown or black pigment, which gives 
its color to the membrane. 

158. Iris, Pupil, and Ciliary Processes. — That 

portion of the choroid coat which lies back of the 
cornea, is separated from it by a considerable space, 
and in this part it takes the name of Iris. The iris 
is a colored curtain, with a circular opening in the 
center called the Pupil. 

On the back of the iris, and 
attached to the outer margin 
of it, is a series of firm, liga- 
mentous bodies, arranged like 
rays around the iris. These are 
the Ciliary processes. To the 
inner end of these is attached a 
number of very fine, muscular 
fibers, with their opposite ends 
inserted into the margin of the 
pupil. When these contract, 
they draw the curtain back, and thus enlarge the 
pupil. 

There is also a set of circular fibers, the contraction 
of which serves to draw the curtain forward, and thus 
diminish the pupil. These motions are produced, in- 
voluntarily, by the effect of light. 

159. The Retina. — The Retina forms the third coat 
of the eye, and lies directly in contact with the vitreous 
humor which fills the greater portion of the ball. This 




a. Pupil, b. Iris. e. Ciliary 
processes. 



116 „ PHYSIOLOGY. 

is a very delicate membrane, made up of a net-work of 
nervous filaments interwoven with minute blood-vessels, 
so as to form a continuous membrane. These filaments 
are expansions of the optic nerve, which, though it is 
the largest nervous trunk in the body, is confined in its 
expansion exclusively to the inner coat of the eye. It 
is limited in its function to the special sense of sight, 
and though so sensitive to the effect of light, it is in- 
capable of feeling the grosser impressions, when in a 
normal or healthy condition; but when inflamed, it 
becomes very sensitive. 

160. Aqueous Humor — its position. — The space 
between the cornea and iris is filled with a transparent 
fluid, which is nearly pure water. It is called the 
Aqueous humor. Its shape is that of a plano-convex 
lens, and it affects the rays of light that enter it in 
precisely the same manner that such a lens does in 
optical instruments. 

In surgical operations on the eye, the aqueous humor 
is sometimes discharged; but if the opening be closed, 
and the light carefully excluded from the eye, the water 
will be reproduced in a few clays. This fluid fills not 
only the space between the cornea and the iris, but 
also that back of the iris, to the suspensory ligament 
of the crystalline lens. 

161. Crystalline Lens. — The Crystalline Lens is the 
principal organ in the apparatus of vision. It is situ- 
ated immediately behind the pupil, and is held in place 
by a thin suspensory ligament, attached to the outer 
margin of the ciliary processes. It is a soft solid, very 
transparent, and, in shape,, a double convex lens, with 
the posterior surface more convex than the front. It is 



VISION. 



117 



Concen- 
tric Layers of 

THkCrYSTA LUKE 

Lens. 




capable o( being Beparated into concentric layers, some' 

what like the coats o( an onion, the T . 

' Pig. 66. 

layers becoming constantly denser as 
we penetrate toward its center. 

The muscular bands attached to the 
ciliary processes have the power of 
adjusting the crystalline lens, so as to 
accommodate the vision to objects at 
different distances from the eye. Back 
of the crystalline lens, the ball of the 
eye is filled with a transparent semi- 
fluid, somewhat resembling the white 
of an egg. It is the vitreous humor, and is in contact 
with the retina at all points. 

Recapitulation. 

Provisions for protecting the eye. Eyebrows, their use. Tears 
secreted by the lachrymal gland, and distributed over the eye- 
ball in winking. Conjunctiva covers the inner surface of the 
eyelid. The eyeball has three coats — the sclerotic coat, the 
choroid, and the retina. The front projection of the sclerotic 
coat is transparent — it is the cornea. The front part of the 
choroid coat is the iris; the opening through it, the pupil. 
The retina, the inner coat, is a nervous membrane. The aqueous 
humor lies between the cornea and iris. The crystalline lens 
lies behind the pupil. 



LESSON XX. 



VISION. 



162. Mechanism of Yision. — The Eye is an optical 
instrument which, by the most perfect adaptation of its 
parts, produces an image of external objects, and casts 



118 PHYSIOLOGY. 

it on a sensitive screen in the back part of a dark- 
ened chamber. It is, therefore, a true camera obscura 
with two lenses, and a very transparent medium be- 
tween the last lens and the retina, where the image 
appears. 

In order to understand how the mechanism of the eye 
operates to produce vision, it will be necessary to state 
a fundamental law governing the movement of light in 
passing through mediums of different density. 

163. Refraction of Light. — Rays of light are thrown 
off from luminous bodies in every direction, and move 
in straight lines so long as they continue to pass 
through the same medium. When light passes from 
one medium into another, as from air into water, the 
ray is bent out of its course, unless it enters on a line 
perpendicular to the surface. 

This bending of a ray out of a straight line is called 
the refraction of light. Different substances have different 
refractive powers. A ray of light passing from the air 
into water, on a line oblique to its surface, is bent 
downward, or refracted toward a line perpendicular to 
the surface of the water; and a ray passing from water 
into the air, is refracted in the opposite direction — that 
is, from the perpendicular. 

164. Reflection of Light from Opaque Bodies.— 

A lens is a transparent medium bounded by curved 
lines. These may make the surfaces either concave or 
convex, and the effect of the lens on rays of light will 
correspond to the shape. A convex lens converges or 
brings the rays together, while the effect of a concave 
lens is to cause the rays to diverge from each other. 
Rays of light are thrown off, not only from luminous 



VISION. 



119 



bodies, but from all substances which afford any obstruc- 
tion to light in passing through them. The latter re- 
flect the rays of light, which thus appear to come from 
the reflecting surface as though it originated there. Most 
bodies are visible, therefore, only by reflected light. 

Fjg. 67.— A Double Convex Lens, showing the Refraction 
of Light. 




a, a. A double convex lens. b. Parallel rays of light, c. The 
focus, or point where the converging rays meet. 

165. Aqueous Humor and Crystalline Lens. — The 

transparent cornea, forming the front of the eye, re- 



Fig. 68.— Formation of Images in the Eye. 

e 




a. The cornea, b. The aqueous humor, c, c. The iris, d, d. The 
sclerotic coat. e. The crystalline lens. /. The optic nerve. 
g. The vitreous humor, h. The pupil. 

ceives the rays of light on a convex surface; and it, 

with the aqueous humor lying back of it, being 
B. P.— 11. 



120 PHYSIOLOGY. 

denser than the air, causes the rays to converge c 
Now rays coming to the eye from objects near it, 
do not reach the cornea parallel with each other, 
but are diverging. This first lens (the aqueous hu- 
mor), therefore, serves chiefly to correct this diverg- 
ence, and bring the light to the crystalline lens in 
parallel rays. This lens is denser than the aqueous 
humor, and consequently refracts the light conveyed to 
it. Both its surfaces are convex, w T ith the back more so 
than the front; therefore the rays, in passing into the 
vitreous humor, are so converged that they form a focus 
on the retina, in the posterior chamber of the eye. 

166. Place and Size of the Image. — Rays of light 
thrown off divergent from every point of an object, 
would therefore be converged to a focus, and form an 
image; and when the eye is properly adjusted, this 
image will be in direct contact with the sensitive 
surface of the retina. This surface transmits the im- 
pression thus made to the brain, where the perceptions 
of it are recorded. 

By a law in optics, the image becomes smaller as the 
distance of the object from the lens is increased. In 
looking at a distant landscape, the whole scene, with 
its mountains, rivers, and forests, covering many square 
miles, is faithfully delineated on a surface scarcely 
more than a quarter of an inch square; and yet so 
perfect is the image of each object, that the mind 
dearly perceives it. 

167. Images on the Retina are Inverted. — But the 

rays of light coming from the lower part of an object, 
will form their focus at the upper part of the image; 
and those from the upper part of the object, crossing 



VISION. 121 

the first, will form the lower part of the image, so 
that the picture will be inverted. 

This is well known to be the position of the image 
formed in a camera obscura, an instrument constructed 
on the princix>le of the eye; and it has been further 
proven by actual experiment. If we take the eye of 
an ox, and carefully dissect the sclerotic and choroid 
coats away from the back part of it, and fit the 
eye thus prepared into an opening in a shutter, so 
that the cornea will look outward, and then place 
ourselves behind the eye, in a dark room, Ave shall 
see the images of external objects in an inverted 
position on its retina. 

168. How Objects are seen Erect. — Many physi- 
ologists have been greatly puzzled to explain why 
objects appear erect, when the images by which we 
see them are inverted; but if we remember that vision 
is an acquired function, and that we learn the position, 
size, and form of things seen, only by habit, the diffi- 
culty disappears at once. 

Universal experience teaches us that the part of the 
image impressed on the lower portion of the retina, 
answers to the upper part of the object; and, reversely, 
impressions on the higher parts of the eye answer to 
the lower portion of objects. Indeed, none of the 
special senses give us knowledge instinctively, but all 
require to be trained and educated, till the perceptive 
powers become familiar with their modes of commu- 
nicating intelligence. 

169. Adjustment of the Eye. — But there is an- 
other difficulty connected with the mechanism of the 
eye, more serious than this. Rays coming from distant 



122 PHYSIOLOGY. 

objects are nearer parallel than those radiating from a 
less remote point, and rays entering the eye least di- 
vergent will come to a focus soonest; consequently, if 
the distance between the crystalline lens and the retina 
were always the same, and the shape of the lens un- 
alterable, we would be able to see objects distinctly 
only in one place. 

If they were nearer to us, the image would fall 
behind the retina; if farther from us, it would be 
formed in the vitreous humor in front of that surface. 
This difficulty is remedied by accommodating the posi- 
tion or shape of the crystalline lens to the distance of 
the object from the eye. The muscular fibers of the 
ciliary processes (§161), draw the lens forward when 
we look at things near us, which movement also com- 
presses the lens, so that its focus is shortened; and 
these joint movements throw the image on the sensitive 
surface of the retina. 

Recapitulation. 

Images are formed in the eye by the refraction of light. 
Self-luminous bodies, and those reflecting light, are objects of 
vision. The aqueous humor corrects the divergence of light; 
the crystalline lens is chiefly concerned in forming the image. 
The distance of the object diminishes the size of the image. 
Perfect vision requires that the image be in contact with the 
retina. Images in the eye are inverted. Position, size, and 
place of an object are determined by habit. The eye adjusts 
itself to the varying location of objects. 



VISION. 123 



LESSON XXI. 

VISION. — CONTINUED. 

170. Spherical Aberration— its cause and effect.— 

The quantity of light admitted into the eye is meas- 
ured by its intensity. In a strong light, fewer rays are 
required to form a distinct image; and accommodating 
itself to this condition, the pupil is diminished by the 
circular fibers of the iris contracting, and drawing the 
edge of the curtain forward. In a dim light, this move- 
ment is reversed, and the radiating fibers of the iris 
draw the edge back, and thus enlarge the pupil. But 
in using the eye with an enlarged pupil in a dim light, 
objects become indistinct, with their outlines no longer 
sharply denned. 

This results from a well-known principle in optics. 
The rays of light which fall near the edge of a convex 
lens are bent more, and consequently have a shorter 
focal distance than those falling near the axis of the 
lens, thus making the focus a line, rather than a point. 
This is called spherical aberration. The contraction of the 
iris covers the edges of the crystalline lens, and thus 
avoiding spherical aberration, leaves the image sharply 
defined when made by a bright light. 

171. Short-sightedness. — Short-sightedness is gen- 
erally attributed to a too great convexity of the cornea. 
In a majority of cases of this kind, the defect in vision 
arises from this cause, but it evidently may be produced 
by a too great convexity of the crystalline lens, as well 
as by the same deformity of the cornea; or there may be 



124 



PHYSIOLOGY. 




The image formed forward of the 
retina. 



Fig. 70.— Long-sightedness. 




too great a distance between the lens and the retina. 
This may be owing to a defect in the power of adjust- 
ment in the eye. If the 
pig. 69,-Short-sightedness. canse f ne ar-sighted- 

ness lies in the cornea, 
age will cure it ; if it is 
from either of the other 
causes, it will remain. 
Long-sightedness arises 
from the opposite condi- 
tions. This is seen in 
the subjoined figures. 

172. Size and Dis- 
tance of Objects — how 
determined. — The abil- 
ity to determine the 
distance and size of ob- 
jects seen is acquired only by practice. The size of an 
object would very naturally be inferred from the space 
occupied by the image on the retina; but a small object 
near the eye will make an image covering as much of 
the retina as a large one at a distance. From this it 
will be seen that size and distance are intimately re- 
lated in vision. 

If we know the distance of an object, we may form 
a pretty accurate judgment of its size; and, on the 
other hand, having determined the size of any thing, 
we readily refer it to the proper distance. Painters 
avail themselves of this law by introducing into pic- 
tures of buildings, landscapes, etc., figures of men or 
animals whose size is well known, and by this means 
they enable us to judge correctly of the distance of the 



The image formed back of the retina. 



VISION. 125 

objects, which the perspective may, perhaps, have failed 
to determine positively. 

173. Transparency of the Atmosphere affects the 
Judgment of Distance. — The degree of distinctness 
in the outlines and general form of bodies, furnishes 
another means of determining distance. This is modi- 
fied very much by the intensity of light and the trans- 
parency of the air. In the clear atmosphere and strong 
light common in mountainous regions, the distance of 
objects is apparently much diminished. 

When we look at objects near to us, the eyes are 
rolled inward, so that the lines drawn through the 
center of each eye will form a greater angle where they 
meet in the object, than they would if it were distant. 
The muscular sense estimates the extent of this inclina- 
tion of the eyes toward each other, and thus materially 
aids in determining distance. 

174. Why Objects are seen Single, when an Image 
is made in each Eye. — When we see objects with 
two eyes, it is evident that two distinct images are 
formed, and yet the mind perceives but one object. 
This depends on our ability to adjust the axis of vision, 
so that the image will occupy exactly the same point 
on the retina in each eye. Any thing that interferes 
with the action of the muscles which roll the eyeballs, 
or that hinders our adjusting the eyes to objects at a 
particular distance, will produce the phenomenon of 
double vision. 

When we attempt to arrange three or more objects at 
different distances from us, so that they shall be in a 
line, we use but one eye, otherwise all the objects but 
one would be seen double. If we press one of our eyes 



126 PHYSIOLOGY. 

so as to hold the ball firmly in the socket, we see all 
objects double, because we interfere with the adjustment 
of the angle of vision. 

175. The Advantage of two Eyes. — The advantage 
of two eyes in seeing is not merely that we double the 
impression made on the nervous center, but we are 
enabled to see more of objects with two eyes than 
with but one. If we place a card before us, with 
its edge directed to the space between the eyes, we 
will see both sides of the card; but if we close one eye, 
the side of the card corresponding to that eye will dis- 
appear. From this simple experiment, it is evident 
that the images in the two eyes are not alike, but they 
must occupy the same point on the retina to make 
vision perfect. 

When we look at a plane surface, each eye has 
exactly the same image in it; but if the surface is 
irregular, curved, or angular, each eye will picture 
its own side of these irregularities; but out of the two 
pictures, the mind perceives one perfect image. 

176. The influence of the Mind on Vision. — In 

cross-eyes, the mind recognizes the image formed in 
but one eye, and thus objects are seen single which 
otherwise would evidently appear double. But it is 
true of ordinary vision, also, that the mind has no per- 
ception of many images that must be formed on the 
retina. Indeed, the whole process of sight is very 
much influenced by the mind, and often the things 
spoken of as objects of sight are really the results 
of our judgment about the sensation. 

Distance, size, and, to a great extent, shape, are rather 
complex judgments than simple sensations. Another 



VISION. 127 

source of false vision is, that the image is not perceived 
at the instant it is made, nor is its absence observed 
the moment it disappears. The separate spokes of a 

wheel in rapid motion blend together and appear con- 
tinuous. So if a burning coal be whirled rapidly in 
a circle, it appears as a continuous line of light, be- 
cause the eye retains the first impression till it is 
reproduced. 

177. Subjective Sensation. — The mind performs an 
important part in all our sensations, as well as in 
vision. What are commonly known as " delusions of 
the senses" are really mental phenomena — morbid 
actions of the perceptive faculties. They are more 
properly called subjective sensations. 

In certain conditions of the skin, there is a percep- 
tion of something creeping on the surface. In many 
diseases, the patient is constantly harassed with certain 
disagreeable tastes or odors. These are perceptions from 
internal conditions, and not from external impressions 
on the organs of sense. Many persons are troubled 
with perceptions of sound, without any external cause; 
but the most wonderful exhibition of subjective sensa- 
tion is to be seen in patients laboring under de- 
lirium tremens, when the most frightful objects are 
pictured to the mind with great distinctness and in 
minute detail. 

Recapitulation. 

Spherical aberration, the effect of enlarging the pupil in a 
dim light. Short-sightedness may be the effect of several 
causes. Distance of an object determined chiefly by its known 
size, and the sharpness oLits outline. Objects are seen singly 



128 PHYSIOLOGY. 

by the image in each eye falling on the same part of each 
retina. More of an object can be seen with two eyes than with 
one. Vision is influenced by the mind. Certain conditions of 
the brain produce false perceptions, or subjective sensations. 



LESSON XXII. 



MOTOR FUNCTION. 



178. The Motor Functions of the Nervous Sys- 
tem. — We have already said (§ 120) that the nervous 
S3 r stem lias a three-fold function ; or, rather, it performs 
three distinct and nearly independent functions. Sen- 
sation is but one of these. By it we become acquainted 
with the external world, and acquire the material for 
thought — that on which the mind exerts its creative 
powers of imagination, comparison, judgment, etc. 
Sensation is thus intimately connected with our ra- 
tional enjoyment; but the power of motion, communi- 
cated to the muscles through the motor nerves, is 
essential to life itself. 

When the heart and the respiratory muscles cease 
to move, death ensues instantly. But the motor func- 
tions have an important bearing on the mental action. 
While the mind receives the thoughts of other minds 
by the sentient nerves, it is able to communicate its 
own thoughts only through the motor nerves. 

179. Voluntary and Involuntary Movements. — 

Muscular motion has been generally considered as of 
two kinds, voluntary and involuntary; or those motions 



MOTOR FUNCTION. 129 

that are immediately under the control of the will, and 
those over which we are able to exert little or no 
control by our volitions. The involuntary movements 
belong to the functions immediately connected with 
life, such as digestion, circulation, secretion, etc. Res- 
piration is a mixed function, controlled to a limited 
extent by the will, but beyond that, becoming invol- 
untary. 

The involuntary motions of the body, when in a 
healthy condition, are carried on without our knowl- 
edge, as well as without our consent. We therefore 
never feel fatigued from the constant action of the 
heart, or the movements of the stomach during diges- 
tion. The wisdom of placing these important functions 
beyond the reach of the will, as w T ell as beyond our 
consciousness, is apparent at the first glance. 

180. Ganglions of Involuntary Motion. — The nerves 
supplying power to the involuntary muscles, do not 
come directly from the brain or spinal cord, but are 
derived from a system of ganglions, or little brains, 
located in the vicinity of the great organs they are 
intended to supply, and these connect with two nervous 
cords extending nearly the whole length of the spinal 
column, and occupying positions on each side of it. 
This double cord is known as the Great Sympathetic 
nerve. These cords are really chains of ganglia, or 
little knots of nervous matter arranged like the spinal 
cord, the gray matter occupying the center, with the 
white matter on the surface. These ganglia are oppo- 
site to the space between the vertebra. They are con- 
nected together by a nervous cord, and each ganglion 
receives a filament from the corresponding spinal nerve 



130 PHYSIOLOGY. 

at its origin, and sends off branches which, uniting 
together, form the ganglia of the involuntary organs. 

181. Importance of Ganglionic Nerves. — The 

branches of this sympathetic system accompany the 
blood-vessels even to their capillary extremities, and 
seem to exert an influence on those mysterious changes 
which take place in connection with this class of 
vessels, such as the secretion of fluids by certain 
glands, direct nutrition of the different tissues, etc. 

This is demonstrated by the effect of injuries to the 
branches of this nervous system distributed to the 
different organs. For instance, if the great semi-lunar 
ganglion, from which the diaphragm derives its nerves 
of involuntary motion, be injured, breathing is so im- 
paired that the patient frequently dies suddenly, as 
if from suffocation. This system has no true sentient 
nerves, but certain mental emotions are referred to the 
larger ganglions, producing peculiar sensations familiar 
to every one. 

182. Passions and Emotions — how expressed. — 

This indirect or sympathetic connection between the 
mental condition and the involuntary organs, gives 
rise to all the common manifestations of emotion or 
passion, such as tears of grief, the paleness of fear, the 
flush of rage, or the blush of confusion or shame. 
These being produced involuntarily by the several 
mental conditions of which they are the exponents, 
can be artificially induced only by exciting in the 
mind the actual condition of which they are the 
proper representatives. 

The actor on the stage, by the long training of, 
perhaps, an originally active imagination, throws his 



MOTOR FUNCTION. 131 

mind into the actual condition of that expressed in 
the character he is personating, and the involuntary 
expressions of these conditions follow, by sympathy, 
as truly as if the emotions were real. 

183. The Physiological Law of Sympathy. — But 

the sympathetic action does not end here. Watching 
the expression of the actor's emotion, our own minds 
become similarly affected, whether we will it or not, 
and that condition is expressed by the invariable 
action of the involuntary nerves. In this power to 
voluntarily call up the mental condition present in 
the exercise of any of the passions, and thus induce 
the true expression of the emotion through involuntary 
functions, consists the chief control of the orator over 
his hearers. 

The speaker who can so impress his own mind as to 
produce the mental state of grief, will find the lachry- 
mal glands responding at once in as copious a flow 
of tears as if his grief were real; and his audience, 
unless they, by a voluntary effort, withdraw their 
attention, and thus sever the cord of sympathy, will 
find themselves weeping too. Such are the mental 
associations of the involuntary nerves. 

184. Degree of Sensibility in the Involuntary 
Organs. — The organs which perform involuntary func- 
tions have, in their healthy condition, no sensibility, 
or, at least, they are sensitive only as they are supplied 
with nerves from the cerebro-spinal system. In certain 
forms of disease, however, the stomach, intestinal canal, 
and heart become exceedingly sensitive to the touch of 
any solid substance. 

Though the will has no direct control over these 



132 PHYSIOLOGY. 

functions yet the activity of the voluntary organs pro- 
duces a decided influence on the rate and force with 
which they act. Brisk exercise, short of the point 
of violence, and not continued to fatigue, will accel- 
erate all the involuntary actions in sympathy with 
the voluntary functions. If, however, the exercise be 
violent, and be carried forward till a sense of fatigue 
is felt, the vital force will be expended on the volun- 
tary organs, leaving the involuntary functions in an 
impaired condition. 

185. Effect of Sleep. — This sympathy of the invol- 
untary w r ith the voluntary movements of the body is 
further seen in the diminished force and activity of 
circulation, digestion, and secretion during sleep, which, 
as w T e shall see in the proper place, is a suspension of 
the voluntary functions. 

Though the involuntary muscles are not capable of 
feeling fatigued, yet they are subject, at least in some 
degree, to the rapid exhaustion which so soon succeeds 
to the forcible contraction of a voluntary muscle. 
Though the heart may continue to perform its function 
incessantly for its "three score and ten" years, yet we 
must remember that its intervals of relaxation are 
equal to its periods of contraction; in other words, 
the heart rests half its time. 



Recapitulation. 

The motor functions are essential to the maintenance of life. 
Muscular motions are of two kinds, voluntary and involuntary. 
The cranial and spinal nerves govern voluntary motion. In- 
voluntary movements are connected with the brain through 



NEBVOUS FUNCTIONS. 



133 



ganglions. The sympathetic nerve, with its connected ganglions, 
controls the circulation, Mention, etc. Passions and emotions 
are expressed through the sympathetic nerve. Voluntary mo- 
tions effect involuntary functions indirectly. 



LESSON XXIII. 



Fjg. 71.— Transverse 

Section of the 
Spinae Cord. 

b 



NERVOUS FUNCTIONS. 

186. Special Functions of the Spinal Cord. — In 

the anatomical description of the brain and spinal cord, 
it was observed that the proportion of gray matter, 
compared with the white, was smaller in the cord than 
in either the cerebrum or cerebel- 
lum. As we come now to inquire 
into the motor function of the 
spinal cord, it will be well to note 
/ G the relative position of these two 
substances. As is shown in the 
subjoined figure, the gray 7 matter 
occupies the center of the cord, 
and is nearly surrounded by the 
white substance. 

Both roots of the spinal nerves 
a. Anterior fissure, b. communicate first with the white 
matter of the cord, but do not ter- 
minate there. Many of their fila- 
ments dip downward through the external white en- 
velope of the cord, and terminate on the gray matter at 
its center. This arrangement gives to the cord a two- 
fold function : 1st. It is, by its white matter, a part of 




Posterior fissure, c, 
c. Gray matter. 



134 PHYSIOLOGY. 

the continuous chain of communication between the 
gray substance of the brain and the motor and sentient 
extremities of the nerves; and, 2d. Under certain cir- 
cumstances, it assumes the functions of brain proper, 
and carries forward its actions unconsciously. 

187. Complex Nature of Voluntary Motion*— Vol- 
untary motion, however simple it may appear, is a very 
complicated matter. If the hand comes into contact 
with a hot poker, an impression is made on the extremi- 
ties of the sentient nerves; this is immediately trans- 
mitted to the spinal cord by the brachial nerve, and, 
through the white matter of the cord, is conveyed to 
the gray substance of the brain, where the sense of heat 
is perceived, and immediately an impulse is transmitted 
to the proper motor nerves by the same route through 
the spinal cord, the appropriate muscles are called into 
action, and the hand removed from its dangerous con- 
tact with a hot surface. That these actions take place 
consecutively can be clearly demonstrated by experi- 
ment, and yet the touch, the sensation, and the motion 
appear to occur at the same instant, 

188. Reflex Motions originate in the Spinal Cord.— 

But the greater number of voluntary motions do not 
originate directly from sensations transmitted to the 
brain, but spring from independent volitions. A vol- 
untary motion, which at first requires a specific action 
of the brain and a clear consciousness of the volition 
which produced it, will, after being often repeated, 
become habitual, and be produced without any con- 
sciousness of the volition commanding it. 

These are called reflex motions, and are supposed to 
originate in the gray matter of the spinal cord, which, 



NERVOUS FUNCTIONS. 135 

in these instances, performs the true functions of brain 
without our being conscious of its action. A great 
majority of the movements of the body belong to this 
class of reflex or unconscious action. 

189. Unconscious nature of Reflex Motions. — 

Movements thus performed fatigue us much less, and 
are usually performed with greater accuracy, than those 
which demand our conscious attention to every volition 
and every motion resulting therefrom. In illustration 
of this, take the example of a walk. At every step the 
foot is carried forward by the contraction of a great 
number of muscles ; but the attention is diverted to the 
scenery around us, or to the particular objects along our 
pathway; or, if not to these, the mind is engaged with 
some train of thought, or in the solution of some 
abstract problem, and at the end of our walk we are 
unable to recall the volition which produced any one 
of the thousands of separate motions we have made, or 
the consciousness of a single step we have taken. 

190. Reflex Motions less exhaustive than Volun- 
tary ones. — When we begin a kind of work to which 
we are not accustomed, our motions are awkward and 
clumsy, and each movement requires our undivided 
attention. They are cerebral motions. But after we 
establish the habit of these motions, however complex 
they may be — or, in common phrase, after we have 
acquired the handicraft — the movements are made 
gracefully, with ease, and without our attention or 
consciousness. These are spinal or reflex actions. 

It is a matter of common observation, that a kind 

of labor to which we are not accustomed, fatigues us 

more than heavier labor to which we have habituated 
B. P.— 12. 



136 PHYSIOLOGY. 

ourselves. This is because cerebral action is more ex- 
hausting than spinal or reflex action. 

191. How the Nerves convey Impressions. — We 

have spoken of the impressions made on the looped 
extremity of a sentient nerve, and of their communi- 
cation along that nerve to the seat of perception in the 
brain, and of the transmission of an impulse or force 
from the same center of influence, along the motor 
nerves to the muscles to produce motion; but our closest 
scrutiny does not detect any matter, however subtle, as 
traversing the nerves in either direction. 

The nervous tissue, like other tissues of the body, is 
made of cells, and those in the white matter of the 
brain, and in the nervous cords, are elongated into 
tubuli, and what is transmitted is probably the mere 
motion or undulation of the molecules of which these 
tubuli are formed. 

192, Communication with the Brain essential to 
Sensation or Motion. — A continuity of nerve structure 
from the brain to the muscles of motion, and from the 
organs of sensation to the brain, is absolutely essential 
to motion or sensation. If the nerve be divided, or if the 
communication with the brain through the spinal cord 
be broken, all the organs to which that nerve is distrib- 
uted will lose the power of either sensation or motion. 

From the fact that the spinal nerves originate by 
separate roots from different tracts of the spinal cord, 
(§ 122,) and of these roots each performs a different func- 
tion, it is possible to lose the power of feeling in a part 
while the function of motion remains unimpaired, 
and the reverse. Both the power of motion and sensa- 
tion may be lost in a limb, while the circulation in it 



NERVOUS FUNCTIONS. \:\j 

will be scarcely disturbed, tins being under the control 
of the ganglionic nerves. 

193, Effect of Injury to the Nervous Trunks.— If 

the trunk of a nerve, at any point between its origin 
and its sentient extremity, be irritated or injured in 
any way, the pain will be referred to the part on which 
the sentient extremities of the nerve are spread. When 
a limb lias been amputated, and the ends of the divided 
nerves left in a condition exposing them to injury from 
compression or irritation, the patient will complain of 
pain in the lost limb; and these unpleasant sensations 
will frequently continue for years. The practical lesson 
to be learned from this is, that sensation is not to be 
received as infallible evidence that the cause producing 
it is located at the point where it is felt. It may be at 
any point along the trunk of the nerve. 

194. Motions Classified. — The motor functions of 
the nervous system may be arranged in three classes: 
1st. Those motions which originate in the gray matter 
of the brain, and proceed from a conscious impulse of 
the will; 2d. Those which at first are voluntary and 
conscious, but by frequent repetition come to be per- 
formed unconsciously, under the control of the spinal 
cord; 3d. Those which are purely involuntary, and of 
which w r e are entirely unconscious. These motions 
originate in the ganglions, and the organs thus acting 
are supplied chiefly with nerves from this source. 

Recapitulation. 

The spinal cord consists, like the brain, of gray and white 
matter, but their relative positions are inverted. Voluntary 
motions are complex. Keflex motions originate in the spinal 



138 PHYSIOLOGY. 

cord. They are performed unconsciously, and are. less fatigu- 
ing than motions of cerebral origin. Sensation and motion re- 
quire unbroken nervous connection with the brain. Injuries 
of nervous trunks produce sensation which is referred to the 
extremities. 



LESSON XXIY. 

MENTAL FUNCTION. 

195. Thought — dependent on the Brain — The 

third function of the brain is thought. In what 
manner the brain acts when one thinks, we may, 
perhaps, never know; and yet we are as certain that 
it is the instrument of thought, as we know its con- 
nection with sensation and motion. Compression of 
the brain suspends consciousness and thought, as cer- 
tainly as compression of the spinal cord arrests motion, 
and destroys sensation in the parts beyond the com- 
pression. 

Certain diseased conditions of the brain derange the 
function of thought, and produce the different forms 
and grades of insanity corresponding to the character 
and intensity of the disease. Malformation of the brain 
may be regarded as a constant accompaniment of idiocy; 
and, as a general rule, the extent of the malformation 
measures the loss of mental power. 

196, Deyelopment of Brain measures Thought. — 

To suppose that the power of thought belongs alone 
to the human race is, perhaps, the most common 
mistake on this subject. There is unmistakable evi- 



MENTAL FUNCTION. 139 

dence that the inferior animals think, and that in 
them the power of thought is more or less perfect, 
according to the degree of brain development. 

In the vertebrate animals, as we ascend the scale 
from fishes to reptiles, from reptiles to birds, from birds 
to mammals, and finally to man, we find at every step 
an advance in the perfection of the nervous system; 
but this advance affects chiefly the cerebrum. Fishes 
have a very perfect spinal cord, the rudiments of a 
cerebellum, but nothing that deserves to be called a 
cerebrum. With them, thought is little more than an 
instinct of self-preservation. In reptiles, the cerebrum, 
though very small, can be clearly distinguished; and 
so the advance continues, intelligence keeping pace 
with it, till it culminates in man. 

197. The Cerebrum, the Organ of Thought, — But 

even in the mammalia, the class to which man, as an 
animal, belongs, the proportion of the cerebrum to the 
cerebellum varies very much. In the lower orders of 
this class, such as the sloth, the ant-eater, and the 
opossum, the cerebrum is but little larger than the 
cerebellum ; but, in man, it is from seven to ten times 
as large. This fact has led physiologists to infer that 
the cerebrum is the proper organ of thought, and the 
inference is probably well founded. 

There is another feature in which the human brain 
differs from that organ in inferior animals. The pro- 
portion of gray matter is much greater in the brain of 
man than in that of any of the lower animals. But 
here, again, we find an ascending scale corresponding 
to the degree of intelligence in the animal. This is so 
uniform, ',hat it may be regarded as establishing a 



140 PHYSIOLOGY. 

general rule, that the proportion of gray, as compared 
with the white matter in the cerebrum, measures the 
sagacity of the animal. 

198. Voluntary and Involuntary Thought.— Within 

certain limits, thought is an involuntary function, but 
beyond these, the intellectual phenomena appear to be, 
to a great extent at least, under the control of the will. 
Thoughts which arise immediately from impressions 
made through the senses are not voluntary, but appear 
to spring up spontaneously. Another source of invol- 
untary thought is found in the appetites and desires 
connected with the maintenance of life and health, 
such as hunger and thirst. 

In the higher and more purely intellectual regions 
of thought, the will exercises at least a directive power 
over the mental action, selecting the subject of thought, 
and determining the direction of the investigation, and 
how far it shall be prosecuted. 

199. Voluntary Thought modified by Training. — 

The power to maintain complete control of the mental 
functions varies materially in different individuals. 
To some extent this variation is natural, but to a 
great extent it is the result of training and edu- 
cation. Every student has observed how much more 
readily and perfectly he can command his attention 
to the subject of his studies, after his mind has 
been trained for }^ears in the daily business of study, 
than he could when he first made his acquaintance 
with books. 

The relation existing between the voluntary and in- 
voluntary departments of thought, gives rise to many 
curious and interesting phenomena. The power to 



MENTAL FUNCTION. 141 

concentrate the thoughts by a voluntary effort, and fix 
them on any line of investigation, is often so strong as 
to completely suppress the involuntary powers for the 
time being. This in common language is called absent- 
mindedness. It may arise from the great force of the 
directive faculty, or from the feeble effect of the sentient 
power on the brain. 

200. Life in the Ascending Scale.— Modern phi- 
losophy assumes that motion, every-where in this world, 
is the result of force, operating on and through matter. 
Gravity, the chemical, electrical, and thermal forces 
pervade the entire material w r orld. In addition to 
these, we "find the force of organic life manifesting its 
presence in the vegetable world by the phenomena of 
nutrition, and through the mysterious process of cell 
growth, molding each individual into a specific form. 
Superadded to this, we have animal life manifested in 
the three-fold function of the nervous system — sensa- 
tion, voluntary motion, and thought. Besides these 
phenomena, man also possesses the power of abstract 
thought, giving him the faculties of imagination, moral 
and religious perceptions, etc. 

201. The Human Powers. — In the possession of 
these human powers, man differs from all the lower 
animals as really as they differ from the vegetable 
world. As the formation of cells and the construction 
of organs, etc., are functions of organic life, and sensa- 
tion, motion, and thought are functions of animal life, 
so abstract reasoning, moral sensibility, the creative 
faculty of imagination, w T ith all its high powers of 
examining and comparing things which are not, as 
though they w r ere, are functions of spirit. 



142 PHYSIOLOGY. 

As animal life differs from the organic, not in degree 
merely, but also in kind, so the power of abstract reason 
differs from animal sensation and intellection — it is of 
another kind. Man manifests all the life forces of the 
vegetable and animal worlds, and in addition to these, 
functions which belong to a higher force, which we 
call Spirit. 

202. Man, compared with the Lower Animals.— 

Of the nature of any force, abstractly, we know nothing. 
Its existence, and the law governing its activities, w T e 
know r only by a careful study of what it does. The 
lower animals have all our senses, and some of these are 
much more acute than in man. They have memory, 
in some instances amazingly perfect; they manifest 
emotions and desires ; and to gratify these desires, they 
adopt means to that end, limiting their reasoning to 
objects of sensation, however, and circumscribing their 
efforts to the securing of pleasurable emotions, and the 
avoidance of painful sensations. But they manifest no 
power to separate and examine, abstractly, the qualities 
of either actions or objects. These are functions of the 
spirit, and in the exercise of these powers man is a 
moral agent : he knows right and wrong ; has a con- 
science, and feels his accountability, and is, therefore, a 
religious being; he reasons on form and number as 
abstract qualities of things, and is, therefore, a mathe- 
matical being. These are attributes of spirit. 

Recapitulation. 

Thought is a function of brain. This faculty is not confined 
to man, but is manifested in the lower animals in proportion 
to brain development. The cerebrum is probably the organ 



SLEEP. 143 

of thought. The sagacity of animals may be measured by the 
proportion of gray matter in the cerebrum. Thought is an in- 
voluntary function, but the directive power is voluntary. 

Abstract thoughts, such as relate to the moral qualities of 
actions, the mathematical properties, form, number, etc., are 
functions of spirit, and belong exclusively to man. 



LESSON XXV. 

SLEEP. 

203. Sleep, as it affects the Tital Functions. — The 

constant activity of the brain, in its triple function, 
rapidly exhausts its power, and, like other living 
organs, it requires rest. But the rest of the brain, 
necessary to restore its wasted energies, like rest in 
other organs, is the suspension of its function. To 
suspend the functions of the nervous system, is to 
induce a state of entire unconsciousness. This is sleep, 
and is a necessity in all animals, as well as in man. 

It is proper to say, however, that the complete 
suspension of function does not extend to the whole 
nervous system. It begins with and belongs properly 
to the cranial brain, extending, by a kind of secondary 
influence, to the spinal cord, and modifying but slightly 
the great sympathetic nerve and its ganglions. There- 
fore, all the involuntary movements of the body con- 
tinue during sleep, but they are performed more slowly 
and with less force. 

204. The order in which Sleep affects the Senses.— 

The transition from a waking to a sleeping state, 

though often very rapid, is a process consisting of 
B. P.— 13. 



144 PHYSIOLOGY. 

several consecutive steps. The progress toward a state 
of sleep appears to begin with impaired sensation, the 
senses of smell and taste being first to feel the effect ; 
after this the eyes close, and vision ceases. The sense 
of touch is early impaired, but does not entirely dis- 
appear until all the other faculties are locked in sleep. 

The sense of hearing maintains its function unim- 
paired as long as consciousness remains ; and there are 
good reasons to believe that, though unconscious of it, 
the auditory sense is constantly reporting to the per- 
ceptive center, though no notice may be taken of these 
reports. A man falls asleep in the middle of a sermon, 
but as soon as the voice ceases he wakes, from the 
auditory nerve ceasing to report to the perceptive 
center. 

205. Cerebral and Spinal Functions differently 
influenced. — While sleep is thus stealing on our 
senses, the power of voluntary motion is early sus- 
pended, especially those motions which demand the 
attention, and which requires each a special volition 
for its performance. The habitual motions, or those 
which are performed by the reflex action of the spinal 
cord, are continued longer, sometimes even after con- 
sciousness is entirely suspended, as in case of persons 
walking. 

Somnambulism, or sleep-walking, is but the waking 
state of the functions under the influence of the reflex 
action of the spinal cord. The involuntary functions, 
such as respiration, circulation, digestion, etc., as soon 
as the voluntary movements of the body are suspended, 
feel the effect at once. The breathing is not so deep, 
and the number of inspirations in a given time is 



SLEEP. 145 

reduced; the pulse is generally diminished in fre- 
quency and force, and the temperature of the body falls 
sensibly. 

206. Effect of Sleep on the Mental Faculties.— 

In the mental department of brain action, sleep first 
impairs the directive power of the mind. By this we 
mean the faculty which determines the course which 
our thoughts shall pursue. Next follow the powers of 
abstract reasoning, imagination, and memory; and last 
of all, the mind ceases to respond to the impressions 
made on the senses, and consciousness of our person- 
ality, or even existence, is lost. 

Just before consciousness becomes extinct, there some- 
times supervenes a curious intermediate state, w r hich in 
common language is called dozing. We are still con- 
scious, but unable to discriminate between impressions 
made by external objects through the senses, and those 
made from within by our own thoughts. This state is 
near akin to dreaming. 

207. Sleep is Brain rest. — In a healthy state of the 
body, after about fifteen hours, more or less, spent in 
brain activity, the nervous system demands rest, to 
recuperate its pow r ers and restore its exhausted ener- 
gies. Sleep is the only true brain rest. We can tem- 
porarily repair an exhausted faculty by suspending its 
action, or exchanging it for some other form of brain 
activity; as, for example, when fatigued with study, 
w 7 e take a brisk walk, thus transferring the action to 
the motor nerves; yet the brain, as a whole, is suffering 
an exhaustion of its force, which can be restored only 
by sleep. 

We may, by a voluntary effort, postpone from hour to 



146 PHYSIOLOGY. 

hour the demanded rest, but, finally, it supervenes 
involuntarily, or inflammation of the brain will ensue. 
Well authenticated instances are on record of persons 
falling asleep on the battle-field, or in the midst of a 
terrible storm at sea, the presence of death itself not 
being able to keep them awake. 

208. How much Sleep is Necessary. — The demand 

for sleep differs materially in different persons. Chil- 
dren require more hours of sleep than do adults, and 
their sleep is more profound, and the suspension of all 
the brain functions is more perfect. As a general rule, 
women endure loss of sleep better than men, and the 
nervous better than sanguine or lymphatic tempera- 
ments. 

Of the three functions of brain, the mental is the 
most exhaustive. Next to this stands the function 
of sensation; and that which demands the least sleep 
is the motor function, or muscular activity. No rule 
can be laid down, with any degree of certainty, pre- 
scribing a given number of hours for sleep in the 
twenty-four. Age, sex, temperament, kind of employ- 
ment, condition of health, etc., will materially modify 
any rule we may adopt. 

209. How far Sleep is Voluntary. — Though sleep 
can not be voluntarily induced, yet w T e may place our- 
selves in such a condition that it will be invited, and 
will almost invariably supervene. Silence, darkness, 
and the absence of any object of sense, together w T ith 
a state of muscular repose, will place the brain in a 
condition where no external demand on its powers can 
be made. In this state of repose, it falls very naturally 
into unconscious sleep, unless this is prevented by the 



SLEEP. 147 

activity of the representative faculties, or the creative 
powers of the imagination. These, in persons of active 
minds, often become troublesome, inducing a state of 
wakefulness which is always exhaustive of the vital 
force, and sometimes causes dangerous disease of the 
brain. 

210. Coma — how it differs from Sleep. — Coma is 
a condition of the brain which, in its external mani- 
festations, resembles very much a profound sleep. But 
in this state, consciousness can not be restored by or 
through impressions made on the organs of sense. 
Natural sleep maybe regarded as an objective condition; 
one by one the senses suspend their functions, and cut 
the brain off from the external world, and thus se- 
cluded, it sinks into a state of insensibility. In coma, 
the brain suffers from mechanical compression, from an 
engorged state of its blood-vessels, from the presence of 
alcohol or some other narcotic, till unconsciousness 
supervenes, and impressions made through the senses 
can no longer arouse it to action. It is in a state of 
subjective sleep. 

Recapitulation. 

Sleep is brain rest, and is common to all animals. It affects 
the involuntary functions only indirectly. Sleep approaches by 
successive steps, affecting the senses in a regular order. 

Somnambulism is the waking state of the spinal cord in its 
reflex functions. Of the mental faculties, the directive power 
first sleeps, and afterward the power to perceive sensations, 
etc. Sleep is involuntary, but may be invited or repelled by 
circumstances. Sleep is an objective condition. Coma is sub- 
jective sleep. 



PART II. 

HYGIENE 



LESSON XXVI. 



HEALTH. 



211. Hygiene defined— the Importance of Health.— 

The art of preserving health is merely the application 
of correct physiological principles to our daily life. 
As we have seen, the human body in living action is 
a very complex piece of machinery. Though wisely 
contrived and admirably constructed for the perform- 
ance of its very complicated functions, yet it is liable 
to derangements both of structure and force. 

The causes leading to these derangements, and the 
circumstances under which they occur, and the mode 
of preventing their occurrence, constitute the science 
of Hygiene ; and its correlate art is the observance 
of such rules of life as will most effectually avoid the 
causes of derangement and disease. The importance 
of this knowledge in practice is so obvious to all, 

(149) 



150 HYGIENE. 

that not one word is necessary on that subject. With- 
out good health, there is neither enjoyment or profit 
in life ; therefore, to secure good health is the first duty 
of every human being; nor can we neglect this duty 
without incurring a fearful responsibility. 

212. Relation of Physiology to Hygiene. — In the 

first part of these lessons we attempted to give the 
student a correct idea of the form and structure of the 
several organs of the human body, and their action in 
a normal or healthy condition. This knowledge has 
two important practical applications : the first of these 
is to preserve health while we have it; the second is. 
to restore it when it is lost. 

If by accident, neglect, or violation of the physio- 
logical conditions of vital actions, whether from ig- 
norance or willful inattention, these actions are im- 
paired, deranged, or disturbed, great skill and knowl- 
edge are required in the physician, in order to restore 
them to the normal condition; but the knowledge and 
observance of a few simple laws constitute the art of 
maintaining health, and these are within the reach of 
all. 

213. False Ideas of Disease — their Influence on 
Health. — The study and practice of hygiene has been 
very much impeded by false notions of the nature of 
disease. In ancient times, diseases were regarded as 
the inflictions of malignant spirits, who entered into 
the living body, deranged the delicate machinery, and 
disturbed its harmonious action. This superstition has 
long since been dispelled by the light of science, but 
there lingers still, in the common mind, the error 
which supposes that disease is a thing — an undefined 



IIKALTII AND DISEASE. 151 

and indefinable something — which has somehow gained 
a lodgment in the body, and is to be driven out by 
medicines. Such notions as these are very unfavorable 
to the introduction of healthful observances in our daily 
life. When the mind has once fully settled in the con- 
clusion that disease occurs by a kind of fatal necessity, 
which no precautions can avail to prevent, and all that 
remains is for the physician to find some specific which 
has the mysterious power of expelling it, but little care 
will be taken to prevent it. 

214. Health and Disease defined. — From a careful 
study of the living body, w T e learn that vital force, if 
not resulting from chemical change, is, at least, its 
constant accompaniment; and the development and 
maintenance of animal power are dependent on vital 
transformations. The lungs are in constant action, 
supplying oxygen to the blood; and the heart keeps 
that blood in incessant motion through all the parts 
of the body. But these sensible and visible motions 
are only accessory to the chemical changes effected by 
the oxygen thus transmitted. 

These changes take place in the tissues of the body, 
and in the combustible elements of our food, evolving 
from the change both heat and vital force. This active 
change and constant renewal of the particles consti- 
tuting the body, is Health; the disturbance, obstruc- 
tion, or perversion of this transformation of the tissues, 
or the imperfect elimination of its products, is Disease. 
It is not a malignant entity, but a morbid action. 

215. Diminished Transformation, a diseased con- 
dition. — A disease may, however, consist in diminished 
or suspended action, as w r ell as in its perversion. In 



152 HYGIENE. 

all diseases of debility, the transformation of the tissues 
takes place too slowly; and nutrition, in all its pro- 
cesses, from the first action of the mouth on the food 
to its final deposition, is impaired, resulting in prostra- 
tion of all the vital forces, and general emaciation of 
the body. 

On the other hand, in febrile diseases the tissues 
are rapidly transformed, and the force evolved from 
this change appears in the correlate form of heat, 
while the tissues thus w r asted are not replaced, as 
nutrition is almost entirely suspended. All narcotic 
substances, such as tobacco, opium, alcohol, etc., pro- 
duce a really diseased condition, inasmuch as they 
diminish the amount of chemical change in the system 
in a given time. Quinine, iron, and kindred sub- 
stances, though they disturb the normal rate of vital 
action by increasing the amount of change, can hardly 
be said to produce disease, as the nutrition is aug- 
mented in the same proportion. 

216. Disease from Perverted Action. — But disease 
may consist in a perverted chemistry of the body, 
resulting in the formation of compounds not found 
in the healthy state of the system. Such are the 
concretions found in and about the joints in gout, the 
gall-stones found in the gall-bladder under certain cir- 
cumstances, and the gravel found in the urinary organs. 
But whatever may be the characteristics of disease, it 
will be found to consist in diminished, accelerated, or 
perverted action, in reference to the chemical change 
going on in the living body. 

The disturbing causes, which thus derange the vital 
action, may not always be within the reach of human 



DURATION OF LIFE. 153 

knowledge, or, if known, may not be under our con- 
trol, yet, in a great majority of cases, we can discover 
and avoid the course of life inducing these derange- 
ments, and thus escape disease. At least, it is easier 
to maintain the normal action than to restore it when 
impaired. 

217. Influence of Hygiene on the Duration of 
Life. — The influence of a knowledge of hygienic laws, 
were that knowledge generally diffused, would greatly 
increase the average duration of human life. It would 
also add very much to the efficiency and value of life, 
both to the individual and to the community, by the 
maintenance of uniform good health, protracting the 
vigor and efficiency of manhood to w r hat we now call 
extreme old age. 

Of the average life of man, deducting infancy, sick- 
ness, and old age, scarcely more than half is available 
for the purposes of active life. Nor should we be sur- 
prised that men and women are so frequently sick, and 
so often unfit for the duties or even the enjoyments of 
life. When w r e observe the almost constant violations of 
the laws of health, so common in every community, we 
wonder that people live at all ; we are surprised at the 
leniency and long-suffering of Nature, in so slowly and 
tenderly exacting the penalty of her violated laws. 

218. Hygiene in relation to the Cure of Disease. — 

But the rules, by the observance of which health is 
maintained, have an important bearing on the cure 
of disease; and it is in this relation that hygiene 
becomes almost as important to the physician as to 
the patient. The persistent violation of a sanitary 
law finally wears out the powers of resistance inherent 



154 HYGIENE. 

in the vital force, and disease follows. No sensible 
physician would even hope for a cure of that disease 
without first restoring an enforcement of the violated 
laws : these being restored and carefully observed, health 
will generally follow with but little aid from medicine. 
The most perceptible change in the practice of medi- 
cine, within the last fifty years, is the diminished con- 
fidence of enlightened physicians in mere medication, 
and their increased confidence in sanitary and hygienic 
measures for the cure of disease. 

Recapitulation. 

Hygiene is the art of preserving health. Disease is deranged 
physiological action. To restore health is a complex and diffi- 
cult work, but to maintain health is comparatively simple and 
easy. Vital force is in the ratio of the chemical changes taking 
place in the body. This chemical action may be too rapid, too 
slow, or it may be perverted. Duration and value of life de- 
pendent on the maintenance of health. Disease arising from 
violations of the laws of health is incurable while these vio- 
lations continue. 



LESSON XXVII. 

FOOD AND DRINK. 

219. Division of the Subject — purposes of Food.— 

In investigating the subject of hygiene, we find it 
convenient to follow the same division which we 
adopted in the first part of the work. We will there- 
fore begin with the hygiene of the Nutritive system. 



FOOD AND DRINK. 155 

This will embrace the subjects of Digestion, Circulation, 
Respiration, and the Transformation of the tissues. 

The subject of digestion includes food and drink, with 
regard, 1st, to quality and quantity; 2d, to the time and 
manner of taking them; and, 3d, to the condition of the 
system. As it is the purpose of food to supply mate- 
rial to repair the wastes of the system from the wear of 
its incessant activities, it is evident that it must contain 
the elementary substances out of which the tissues of 
the body are formed; for the vital and chemical forces, 
however strangely they may change and modify the 
forms of matter, can create nothing. Therefore our 
food must furnish the material for growth and repair. 

220. Organic and Inorganic Substances. — In gen- 
eral terms, we may assume that all digestible food is 
derived from the organized forms of matter, vegetable 
or animal. It is true that a number of substances, 
such as water, common salt, lime, etc., enter into both 
the fluids and solids of the body; but these undergo 
no change by digestion. They enter the circulation by 
absorption, maintaining their true forms, and are never 
vitalized in the same manner that muscles, nerves, and 
membranes are. Yet we must not suppose that these 
are therefore unimportant in the animal economy. 

The inorganic elements of the body are, indeed, indis- 
pensable to its growth and health. Of these, water is 
by far the most abundant, and, we may safely say, of 
the most immediate importance. It is the solvent of 
all that goes into or is carried out of the system. It is 
present in all the tissues, and permeates even the 
firmest solids, carrying nutrition to them, and bearing 
from them the waste material. 



156 HYGIENE. 

221. Sources of Impurity in Water.— Water, to be 

^fitted for the purposes of the body, should be as nearly 
pure as possible ; but absolutely pure water can be ob- 
tained only by distillation. Rain-water, in falling 
through the air, absorbs carbonic acid, ammonia, and 
other gases, which are mixed in minute quantities 
with the air; afterward, in percolating through the 
earth, it dissolves variable amounts of lime and other 
mineral substances which are found in solution in the 
water of our springs and wells. 

But, fortunately, the gases from the air or the min- 
erals from the earth are not often in such quantities 
as to greatly impair the healthfulness of water as a 
diet drink. Much has been said of the unhealthfulness 
of what is called hard ivater, but a comparison of lime- 
stone and freestone districts shows much less difference 
in the health of the people living in them, than we 
might expect. 

222. Lime, how held in Solution — Rain-water. — 

Water holds lime in solution chiefly by aid of the 
carbonic acid dissolved in it; but on raising the tem- 
perature of the water, the carbonic acid escapes as a 
gas, and the lime is consequently precipitated. It is 
probably from this cause that limestone water is com- 
paratively harmless. As soon as it enters the stomach, 
the temperature rises till it reaches blood-heat, the 
carbonic acid escapes, and the lime is precipitated, 
and, being indigestible, is carried off by the intes- 
tines. 

Iron is frequently found in spring and well waters, 
but it is seldom in such quantity as to materially 
affect its healthfulness; and when such is the case, 



FOOD AND DK1NK. 157 

it imparts to the water an offensive taste, which will 
commonly prevent its use for drinking purposes. 
Rain-water, well filtered through alternate layers of 
coarsely pulverized charcoal and clean silicious sand, 
furnishes a diet drink sufficiently pure for all practical 
uses. 

223. Organic Impurities in Water. — But organic 
impurities, derived from decomposing animal and veg- 
etable matter, are much more injurious than the ordi- 
nary mineral impurities in water. Unfilterecl rain- 
water, especially if it has been collected from a wooden 
roof, is generally unfit for drinking or culinary pur- 
poses; and river water is seldom so free from organic 
substances, in solution, as to render it fit for table or 
kitchen use. 

Rivers, springs, and shallow wells often become im- 
pure from sewage which is mixed with them in the 
vicinity of large cities. Sickness is sometimes induced 
by the use of such water, when neither the taste nor 
smell of it betrays the presence of the impurities. It 
is hardly necessary to add that surface water, though 
derived from recent rains, and drawn from the surface 
of clean meadows or woodlands, is unfit for use until it 
has been very thoroughly filtered. 

224. Proper Temperature of Drinks. — For drinking 
purposes, water should have a temperature ranging 
between fifty-five and sixty degrees Fahrenheit. A 
temperature above sixty is not palatable, and a lower 
temperature than fifty-five degrees is injurious to the 
stomach, and often dangerous. Especially is this true 
of ice-water used at meals. Food requires a temperature 
varying but a few degrees from blood-heat (ninety- 



158 HYGIENE. 

eight), to insure its rapid and perfect digestion; but 
if the drink used at meals be either ice-cold or boiling 
hot, digestion will be suspended until the contents 
of the stomach has acquired nearly the natural tem- 
perature of the body. 

Both ice-water and hot drinks at meals are un- 
healthy, but of the two, the former is the most inju- 
rious. In warm weather, when heated from exercise, 
ice-cold water should never be used, and even water 
at the proper temperature should be taken slowly 
and with caution. 

225. Tea, Coffee, and Chocolate.— The diet drinks, 
tea, coffee, and chocolate appear to have been mis- 
understood until very recently. They have generally 
been classed with stimulants and narcotics, but care- 
ful experiments have established the fact that their 
action is to hasten the transformation of the tissues, 
as is indicated by the increased volume of carbonic 
acid exhaled from the lungs in a given time, when 
under their influence. The active principle in each 
of these belongs to that family of vegetable alkaloids 
of which quinine is the representative. 

But it is not to be inferred from this that every 
indulgence in these beverages is harmless. Tea and 
coffee, besides the active principle, contain a large 
amount of astringent matter (tannic acid), which acts 
unfavorably on the mucous membrane of the stomach 
and intestines. This is, however, modified to a great 
extent by the action of milk, which should always be 
used with these beverages. 

226. Fermented Drinks — their effects. — Beer, ale, 
wine, and other diet drinks produced by fermentation, 



FOOD AND DRINK. 159 

and consequently containing alcohol, should be uncon- 
ditionally rejected by every one who wishes to main-* 
tain good health. It is the characteristic action of 
alcohol to prevent or arrest chemical change in organic 
substances. But digestion is chemical change, and so 
long as the alcoholic mixture is mingled with the food, 
that change is suspended. 

The absorbents of the stomach, however, soon remove 
it into the circulation, but the effect of its specific 
action on the nerves of the stomach remains, diminish- 
ing and perverting the sensibility of that organ, so that 
the food in a half-digested state is hurried into the in- 
testines, and the nutriment is lost, if nothing w r orse 
occurs. The glass of wine at dinner is merely a bribe 
to deaden the sensibility of the stomach, overloaded by 
gluttonous indulgence, so that it may not complain. 

Recapitulation. 

The subject of digestion, as it relates to food, embraces quan- 
tity, quality, time and manner of taking, and the condition of 
the system when food is taken. Inorganic substances undergo 
no change by digestion. Impurities in water, and the sources 
from which they are derived. Mode of purifying rain-water. 
Extremes of temperature in drinks — their effect on digestion. 
Tea, coffee, and chocolate — their true character. Fermented 
drinks are always injurious. 
B. P.— 14. 



160 HYGIENE. 

LESSON XXVIII. 

CLASSIFICATION OF FOOD. 

227. Animal and Vegetable Food— their essential 
identity. — The classification of food into animal and 
vegetable, which appears so obvious and which, a few 
years ago, was so generally admitted, is found, on care- 
ful examination, to be without any real foundation. 
Animal substances are all derived from the vegetable 
kingdom, and most of the proximate principles entering 
into the composition of animal bodies are found already 
formed in vegetable organisms. The prejudice against 
animal food is therefore without foundation, so far as 
the chemical constituents of the food is concerned. 

Animal food is only a more concentrated state and 
differently organized form of the same substances we find 
in vegetables. The vegetable world, however, contains 
many proximate elements that are not transferred to 
the animal kingdom. No one substance, whether pro- 
duced in the vegetable or animal kingdom, contains all 
the material of healthful, nutritious food; nor do all 
persons require the same proportions of the various 
kinds of food, nor does the same person under different 
circumstances. 

228. The Three Groups of Food. — Food may be 
conveniently divided into three groups, according to 
their resemblances in composition, and the general 
purpose which they subserve in the animal economy. 
These are, 1st. The Proteine or flesh-forming group; 
2d. The Amylaceous or starchy group; 3d. The Ole- 
aginous or fatty group. 



CLASSIFICATION OF FOOD. 1G1 

In their office as food, the second and third group, 
though not identical, are nearly allied to each other. 
The old division of food into the carbonaceous or heat- 
producing substances, and the nutritious or flesh-form- 
ing materials, is found to be faulty, inasmuch as the 
latter, in its chemical changes, also gives off heat, and 
the changes in both are connected with the evolution 
of vital force. 

229. The Proteine Group— its several substances.— 

The proteine group consists chiefly of gluten, ftbrine, 
albumen, and caseine. These all contain nitrogen, and 
closely resemble each other in their chemical compo- 
sition, though they differ materially in the form of 
their organization and in their general appearance. 
They decompose by putrefaction, and give off in that 
process the disagreeable odor familiarly known as ac- 
companying that kind of decay. 

Gluten is found in various kinds of grain, in fruits, 
and in numerous vegetables, such as asparagus, cab- 
bages, etc. It is easily obtained by washing the starch 
from flour with cold water. It is a tough, elastic sub- 
stance, of a light gray color, without odor, and with a 
slightly sweetish taste. Its composition is the same as 
that found in the lean flesh of animals, the two differing 
only in the manner in which they are organized. 

230, Fibrine, Albumen, and Caseine. — Fibrine is 
found in solution in the blood of animals, and is pre- 
cipitated when the blood is cooled, forming the essential 
part of the coagulum, or clot, from which it may be 
obtained by washing with cold water. It is the sub- 
stance from which most of the fibrous tissues of all 
animals are formed. 



162 HYGIENE. 

Caseine is the curd or solid part of milk, which is 
separated by coagulation, and therefore forms the chief 
ingredient in cheese, as it is the chief element of nutri- 
tion in milk. It is found in the seeds of many plants, 
such as peas, beans, etc. Albumen is found nearly 
pure in the white of eggs. It dissolves, to a limited 
extent, in cold water, but coagulates and hardens in 
water a little below the boiling temperature. It occurs 
in nearly all the fluids of the living body, and forms a 
large proportion of the brain. It has also been detected 
in the seeds of many vegetables. 

231. Gelatine — its properties and use. — Gelatine, a 
substance often associated with this group, differs essen- 
tially from those just described, both in chemical com- 
position and in material form. The animal matter in 
bones, the substance of tendons, ligaments, etc., is gela- 
tine. Glue is the form in which it is most familiar. 
While the true proteine compounds are convertible into 
one another in the animal economy, gelatine can not be 
appropriated to any purpose but the formation and 
repair of bone, tendon, ligament, etc. 

It is sparingly soluble in cold water, but dissolves 
readily in that fluid at or near the boiling point. It is 
the essential ingredient in soups and animal jellies. 
The fact that it can not be appropriated to the repair 
or growth of the soft tissues of the body, corrects a 
popular mistake in regard to the very nutritious 
quality of soup. 

232. The Tissues — whence derived. — All the tis- 
sues of the body are derived from the proteine group 
of alimentary substances and from gelatine; conse- 
quently their growth and constant repair depend on 



CLASSIFICATION OF FOOD. 163 

a sufficient supply of these, in such form and condi- 
tion as will enable the stomach most readily to digest 
them, and place them in favorable circumstances to be 
assimilated. It is of but little consequence whether 
they are derived from their original forms in the vege- 
table world, or from the secondary forms of animal or- 
ganization, but it is of the first importance that these 
be in a sound condition, entirely free from any taint 
of decomposition or putrefaction. 

Animal food is usually preserved from decay by an 
excess of salt (chloride of sodium), which requires to be 
dissolved out by the fluids of the stomach before diges- 
tion takes place. Salt meats are therefore not so readily 
digested as fresh. 

233, The Amylaceous Group — its office. — The 

second group of alimentary substances comprises starch 
and the several forms of sugar, gums, etc. From this 
group is derived by far the largest bulk of our food; 
and in whatever form it comes to us, it is the product 
of vegetable life. All the members of this group con- 
tain the same chemical elements, and differ only in the 
proportions in which these are combined. They are 
especially rich in the two combustible substances, car- 
bon and hydrogen. This fact indicates the office of the 
starch and sugar, which, in the form of bread, potatoes, 
fruits, and other vegetable productions, enter so largely 
into our daily bill of fare. 

In combining w r ith the oxygen inhaled by the lungs, 
these undergo a true combustion. From this source, 
and from the oxidation of the waste matter of the 
tissues, are derived the animal heat and working force 
expended by the body. 



164 HYGIENE. 

231. The Oleaginous Group— the use of Oils and 

Fats. — The oleaginous group consists of various oils 
and fats, derived both from the vegetable and the 
animal world. Like the members of the other groups, 
they are closely allied to each other in composition, 
and are convertible each into the other in the vital 
economy. The oils are non-nitrogenized bodies, made 
of the same elementary substances as those composing 
the second group, but containing much less oxygen. 
They therefore form the highest grade of heat-producing 
food, and are in demand in cold temperatures and 
with those exposed to the winter climate of the tem- 
perate zones. Fatty matter is also found in the brain, 
and is probably an essential constituent of that impor- 
tant organ. 

Recapitulation. 

Animal and vegetable forms of food contain the same proxi- 
mate elements. Food is divided into three groups — the pro- 
teine, the amylaceous, and the oleaginous. The tissues are 
derived from the proteine forms of food. The proteine ele- 
ments are formed in vegetables and transferred to animals. 
The amylaceous group supplies the largest portion of our daily 
food. Both the amylaceous and the oleaginous groups furnish 
heat-producing food. They consist chiefly of combustible ele- 
ments. 



QUALITY OF FOOD. 165 



LESSON XXIX. 

QUALITY OF FOOD. 

235. Volume of Food important. — Before we pro- 
ceed to name the several articles of food which go to 
make up our bill of fare, it may be well to say, that the 
value of any particular article does not depend alto- 
gether on the amount of nutritious matter it contains. 
Nutriment may be so concentrated or so combined as to 
render its digestion difficult, if not impossible. 

The stomach requires a certain degree of distention 
for the ready and perfect performance of its function. 
To secure this distention, volume or bulk in the food 
is required, at least to a certain extent. An ounce 
of concentrated nutriment mixed with half a pound 
of inert, indigestible matter, will generally be digested 
much more readily than if it were taken unmixed. 
The nutritious elements of food may be so combined 
as to render their separation difficult, and consequently 
their digestion slow and imperfect. 

236. Milk as a perfect Diet. — Milk comes nearer 
supplying all the demands of a complete nutrition than 
any other substance. It has, therefore, been generally 
regarded as the perfect type of food, and other articles 
have been measured by this standard. This, however, 
is true only of young or growing persons ; but in adults 
engaged in active and laborious employments, it fails 
to furnish a necessary proportion of combustible or 
heat and force-producing elements. 

Milk from different animals varies considerably in its 
composition, and even from the same animal, under 



166 HYGIENE. 

different circumstances of food, exercise, temperature, 
etc., a considerable variation in quality is observed. 
The average of a number of specimens of milk, taken 
from several cows, gives, in a hundred parts, 4.48 
parts of caseine or cheesy matter, 3,13 of butter, 4.47 
of sugar of milk, .60 of saline matter, and 87.32 of 
water. 

237. Milk, by what circumstances modified. — In 

most stomachs, milk is more digestible when quite 
fresh, but there are conditions of that organ in which 
the lactic acid, formed when milk coagulates, is re- 
quired to supplement the deficiency of acid in the 
gastric fluid. This relates, however, to a morbid and 
not to a normal condition of the digestive organs. Milk, 
when used as a diet drink, should have a temperature 
not lower than sixty degrees. 

Iced milk, taken at meals, suspends the digestion of 
the food till the whole mass has acquired the natural 
temperature of the body; and sometimes this interrup- 
tion so disturbs the whole process, that the work is very 
imperfectly done. Milk is much affected by the food 
of the cow producing it, and certain odors, such as 
clover-bloom and others less agreeable, can readily be 
detected in the milk when fresh. From this cause, 
decaying or putrescent food and slops should never be 
fed to cows giving milk. 

238. Cheese and Butter — their dietetic value. — 

Cheese is a product from milk, and contains, when 
properly made, the caseine and most of the butter, 
together with a considerable proportion of the milk 
sugar. It is a highly concentrated form of food, and 
therefore it should never be eaten alone, but always 



QUALITY OF FOOD. 107 

with the more crude and bulky forms of vegetable 
diet. Mixed in tins manner, cheese digests readily, 
and furnishes a large amount of material for repairs 
in active bodies. Taken by itself, it is hard of diges- 
tion, and often produces serious disturbances of the 
stomach. 

Butter is a true fat, but more complex in its char- 
acter than the other oils, whether animal or vegetable; 
and from this cause it is more liable to chemical 
changes, producing certain acids which give the rancid 
character to it, and greatly impair its dietetic value. 
It is purely a heat and force-producing article, and 
furnishes nothing to growth or repair. 

239. Eggs very nutritious — how to cook them. — 

Eggs consist chiefly of albumen and the mineral salts, 
especially those whose acids are derived from phos- 
phorus and sulphur. They are, therefore, a very per- 
fect but a very concentrated form of food. However, 
albumen is the most digestible form of all the proteine 
group, and eggs, if properly prepared, seldom fail to be 
digested, though taken alone. 

Mixed with a proper measure of food containing 
starch, so as to increase the bulk and furnish an 
additional supply of the heat-producing material, there 
is no more nutritious and healthful diet than fresh 
eggs. Those of barn- yard fowls are always to be pre- 
ferred to the eggs of water fowls. Eggs, though very 
nutritious in themselves, are often so injured in cook- 
ing as to render them almost indigestible. By what- 
ever method they are cooked (and boiling is the best), 
the white should be merely coagulated and the yolk 
left soft. 

B. P.— 15. 



168 HYGIENE. 

240. Animal Flesh — kinds and value. — Animal 
flesh furnishes a concentrated and highly nutritious 
food. In most of its forms it is easily digested and 
readily assimilated. There is quite a wide margin, 
however, between different kinds of meat, in regard 
to the amount of available nutrition, as well as to 
the ease with which they are digested and incorporated 
into the living tissues. 

Beef, pork, and mutton are the most common forms 
in which animal flesh is met with on American tables. 
Of these, mutton is the most digestible, but beef con- 
tains the highest per cent of nutriment. Pork is of 
value chiefly for the large amount of oil it furnishes, 
and its consequent high, heat-producing qualitj^. It 
is therefore well adapted to use in cold climates and 
in the winter season. The animal fats should be used 
with caution and sparingly in warm weather, but never 
in hot climates. 

241. Necessary Precaution in Fattening Animals 

for Food. — The flesh of young animals is more easily 
digested than that of the more mature. An important 
exception to this rule may be mentioned : beef is more 
digestible than veal. The good quality of meat depends 
much on the manner in which it is fed and prepared 
for the market. The best beef is fattened on fresh 
pastures, with but little grain. This mode of fattening 
tends to develop the muscular or fleshy part of the ani- 
mal, and diffuse the fat through the flesh, rather than to 
accumulate it in masses, as is done in stall-feeding. 

Animals fattened on the slops of distilleries and the 
wastes of breweries are entirely unfit for food, and 
should not be offered in the markets. Animals taken 



QUALITY OF FOOD. 169 

to market by long journeys, whether on foot or in 
crowded cars, arc not suitable for food till they have 
fully recovered from the journey. 

242. Wholesome Meat — how distinguished. — The 
flesh of good beef, pork, or mutton should be a light 
red, approaching toward the scarlet hue. A pale color 
indicates an immature animal, and dark red meat 
shows an animal too old and tough to be savory, or 
that it had been suffering from the effects of a long 
journey to market. 

Wholesome meat should be entirely free from even 
a tendency to putrefaction. This can not always be 
detected by the odor, for meat kept on charcoal or on 
ice will frequently be far advanced in the first stages 
of decomposition, and yet emit no unpleasant gases. 
If, on cutting the flesh, the surface appears mottled, 
or marbled with pale spots, and if the fibers be easily 
torn across, it will be safe to reject such meat. The 
fat of pork and mutton should be white and firm, even 
in warm weather, and that of beef but slightly tinged 
with yellow. 

Recapitulation. 

Concentrated food is difficult of digestion. Milk is a perfect 
food only for growing persons. The composition of milk. It 
varies with the circumstances of the animal from which it is 
derived. Cheese is a very concentrated form of food, and 
therefore should never be taken alone. Butter belongs to the 
oleaginous group. Eggs form a very nutritious diet, and when 
properly cooked, are easily digested. Animal flesh — difference 
in the several kinds. The kind of food on which animals are 
fattened affects the quality of their flesh. 



170 HYGIENE. 



LESSON XXX, 

QUALITY OF FOOD — CONTINUED. 

343. Flour— its composition— different varieties. — 

The amylaceous or starchy group is represented chiefly 
by the cereal grains, such as wheat, rye, Indian corn, 
barley, etc. Of these, wheat is the most important, 
as it approaches nearer to a perfect diet than any 
other product of the vegetable world. Different samples 
of wheat vary somewhat in the proportions of the dif- 
ferent proximate elements entering into its compo- 
sition. 

This arises from the many varieties of wheat cul- 
tivated, and from the quality of the soil on which it 
is grown. The average may be stated at twelve per 
cent of gluten, seventy per cent of starch, and ten 
per cent of water; the remaining eight per cent consists 
of sugar, oil, and phosphates of lime, potash, and mag- 
nesia. These proportions are seldom found, however, 
in fine flour. The central portion of the grain consists 
almost entirely of starch, while the outer part, near 
the cuticle or bran, is rich in gluten and the mineral 
salts. In the common methods of manufacturing flour, 
these are chiefly lost, by not being made fine enough 
to pass through the bolting cloth. 

244. Adulteration and Deterioration of Flour. — 

From this cause, very fine flour is less nutritious 
than that of a coarser grade. Brown bread, made of 
unbolted flour ground closely, contains all the nutri- 
ment of the grain in a very digestible form; and for 
persons of feeble digestive powers, it is always to be 



QUALITY OF FOOD. 171 

preferred to fine bread. Flour is sometimes adulterated 
by mixtures of carbonate of lime or chalk. This can 
be detected by a grittiness in chewing the flour or 
the bread made from it. 

Adulterations from mixture of cheaper grains are 
difficult to detect, but, fortunately, they are of less 
consequence, as they but slightly diminish the nutri- 
tive value of the food. Flour becomes whiter by age, 
but this improved appearance is at the expense of its 
sweetness and real value. The richer flour is in gluten, 
the more rapidly it deteriorates. 

245. Rye and Corn as Bread Materials. — Rye 

furnishes a wholesome bread, though it is much darker 
than that made from wheaten flour. It contains more 
sugar and oil than wheat, has a heavier bran and a 
smaller proportion of starch. In the gluten, the nitro- 
genized matter resembles caseine from milk, w r hile that 
from wheat flour more nearly resembles fibrine. In del- 
icate stomachs it is not easily digested; and it is much 
more difficult to make good bread from rye than from 
wheat flour. 

Indian corn contains a larger proportion of oil than 
any other grain known. This, however, differs very 
materially in the different varieties of corn. Those 
known as flint corn yield more than double as much 
oil as the varieties with large, spongy grains. The 
quantity of sugar, also, is far from being constant. 
It is very rich in starch, but in the nitrogenized or 
flesh-producing element, it is poorer than any bread 
material in use, excepting, perhaps, buckwheat. This 
is not in the form of gluten, as found in other grains, 
but in a peculiar form called zeine. 



172 HYGIENE. 

246. Preparation of Corn for Food, — From these 
peculiarities it lacks the adhesive qualities of dough 
from wheat or rye flour, and therefore the bread is 
made light by fermentation, with difficulty. In pre- 
paring articles from corn meal, a longer time is re- 
quired to cook them thoroughly than is necessary when 
other bread materials are used. But when properly 
cooked, corn meal furnishes a palatable, highly nutri- 
tious, and easily digested food. 

Barley and oats are but little used as bread material 
in this country, though in some parts of the world 
they form an important part of the daily food of a 
large population. They are rich in sugar and gluten, 
but poor in starch and the phosphates, as compared 
with wheat. Rice is seldom used for bread. It is very 
digestible, consisting of nearly pure starch, with the 
smallest quantity of gluten and oil. 

247. Beans and Peas — their dietetic yalne. — Peas 

and beans can hardly be classed with this group, as 
they contain from twenty-five to thirty per cent of 
nitrogenous matter, in the form of vegetable caseine; 
but as there appears to be no more appropriate place 
for them, w T e have assigned them here. They are highly 
nutritious, but, like most other concentrated forms of 
nutritive matter, they are hard to digest, and if not 
readily digested, they are apt to produce flatulency and 
other derangements of the digestive apparatus. Taken 
in the unripe state, they are less objectionable in this 
respect. 

As a substitute for animal food, to laborers and others 
following active employments, there is no form of veg- 
etable food so well adapted as peas and beans. They 



QUALITY OF FOOD. 173 

are rich in sulphur and the phosphates, and contain 
Blifccient starch to furnish heat-producing material 
even for winter food. 

218. Potatoes — their composition and use as 
Food. — There is a class of succulent vegetables ex- 
tensively used as food, which is allied more or less 
remotely to this group of starchy foods. The potato 
properly stands at the head of this list. Well matured 
potatoes contain, in one hundred parts, seventy-four 
parts of water, twenty-three parts of starch, one and 
one-half parts of gluten, and one part earthy salts, 
with but a small fraction of oil. It will be observed, 
the proportion of flesh-producing material is very 
small. They should, therefore, always be associated 
with animal food to supply this defect, as well as 
that of the oily matter. 

Potatoes, when properly cooked, are easily digested; 
and being a bulky form of food, are w r ell adapted to 
accompany the more concentrated articles of diet, not 
merely to give distention to the stomach, but to pro- 
mote the digestion of those highly nutritious articles 
that are often difficult of digestion. 

249. Other Succulent Tegetables. — Turnips, beets, 
carrots, and parsnips, constitute an important group 
in this class of succulent vegetables. They contain 
even more water than potatoes, and the solid part 
consists largely of sugar, instead of starch, and the 
proportion of nitrogenous elements is somewhat larger 
than in the potato. They are rather hard of digestion, 
and should be used sparingly by persons whose habits 
of life are not very active, or whose digestive powers 
are feeble. 



174 HYGIENE. 

Asparagus, onions, and cabbage contain but little 
starch. They are, however, well supplied with the 
flesh-forming elements, and are therefore very nutri- 
tious when properly prepared. Onions contain an es- 
sential oil, on which their peculiar odor depends. This 
oil is indigestible, but being volatile, it is absorbed 
from the stomach, and passing to the lungs, is exhaled, 
giving the disagreeable odor to the breath. Thorough 
boiling removes the greater portion of this, and leaves 
a very nutritious food. 

250. Fruits — their importance as diet. — Fruits 
consist mainly of water, with variable quantities of 
starch, sugar, and gum. Many kinds of fruit furnish 
a fair supply of gluten, and are on that account highly 
nutritious. Their chief value, however, as diet, is in 
the various forms of vegetable acid which they contain, 
in such combination with the alkaline and earthy car- 
bonates, as supply an important want in the process 
of digestion, as well as furnish the lime and potash 
which they contain for the use of the animal economy. 

Most of these acids are laxative, and are therefore 
well adapted to persons predisposed to habits of con- 
stipation. This is especially true of the malic acid, 
which abounds in apples, peaches, pears, etc. The 
tartaric acid, so abundant in grapes and berries gen- 
erally, is not only a laxative, but tends to increase the 
secretion of the skin and kidneys. 

Recapitulation. 

The amylaceous group is represented chiefly by the cereal 
grains. Wheat is the most important of these. Fine flour is 
not so nutritious as coarse. Flour deteriorates "by age. Rye 
contains more sugar and oil than wheat, but a smaller propor- 



MODE OF PREPARING FOOD. 175 

tion of starch. Indian com ifl rich in oil and starch. Its nitro- 
genous element has a peculiar form. Beans and peas arc very 
nutritious, but hard to digest Potatoes are rich in starch, hut 
deficient in the proteine elements. Asparagus, onions, and cah- 
ge arc Lacking in starch, hut abound in proteine elements. 
Fruits are important on account of the acids they furnish to 
assist digestion. 



LESSON XXXI. 



MODE OF PREPARING FOOD. 



251. Cooking Food — what is gained by it. — The 

natural quality of the different articles of food is 
scarcely less important than is the mode of preparing 
them for the table. But few articles of diet are fit for 
food without some preparation. This is usually done 
by the aid of heat. Cooking, when properly performed, 
accomplishes two objects: 1st. By rendering the sub- 
stances soft, they are easily masticated, and more read- 
ily dissolved in the gastric fluid; and, 2d. The peculiar 
flavor of the food is developed, so that it is more agree- 
able to the taste. 

This is generally the result of cooking, though there 
are some very well marked exceptions to the rule. 
For example, cabbage cut fine, and dressed with di- 
luted vinegar, is more digestible than when cooked in 
any form. The flavor of some kinds of fruit is so 
volatile that it escapes in cooking, and thus the fruit 
is rendered insipid. Long continued boiling produces 
this effect on nearly all kinds of vegetables. 

252. Meat — general rule for cooking it. — Meats 
are prepared for the table by several methods, such as 



176 HYGIENE. 

boiling, roasting, baking, broiling, frying, etc. One 
general rule applies to all these methods, and its ob- 
servance is indispensable if we would preserve the 
good qualities of flesh. 

All wholesome meats contain a good proportion of 
albumen. This substance is familiar to us in the white 
of eggs. It dissolves readily in warm water, but if the 
temperature be raised to near the boiling point, it is 
instantly hardened, and becomes entirely insoluble in 
water. To preserve this property of meat is essential 
alike to its nutritive quality and good taste. A high 
heat should therefore be applied to meat at the begin- 
ning, and as the cooking proceeds, the heat may be 
reduced. This coagulates the albumen on the outside, 
and thus prevents the escape of the nutritive juices. 

253. Boiling Meat — the Rules. — When meat is 
cooked by boiling, the pieces should be large, and the 
water raised to the boiling point before the meat is put 
in. By this means its flavor may be preserved nearly 
perfect, and the loss in weight greatly diminished. 
This, in the ordinary method of boiling meat, amounts 
to nearly one-third of the original weight. After boil- 
ing rapidly for ten minutes, the heat should be lowered 
to about one hundred and seventy degrees, or to a point 
below any perceptible boiling, and should be retained 
at that temperature till the fiber is fully softened and 
tender. 

If the object is to make soup, the meat should be 
put into cold water, and the temperature of about one 
hundred and fifty degrees maintained for two or three 
hours, when a few minutes of rapid boiling will com- 
plete the process. Soft water is a better solvent than 



MODE OF PREPAKING FOOD. 177 

hard, therefore soup should be made with soft water, 
and the salt should not bo added till the last stage 
of the process. The opposite course should be followed 
when meat is boiled for other purposes. 

254. Roasting, Broiling, Baking, and Frying 
Moat. — Meat is cooked with a direct application of 
heat by roasting, broiling, or baking. By either of 
these methods the flavor of the meat is better retained 
than when cooked by boiling, but care must be taken 
not to overdo the cooking, and thus render the fiber 
hard, insipid, and indigestible. The same rule should 
be observed in the application of heat when cooking 
meat by these methods as by boiling (§ 253). 

Frying is in all respects the worst method of cooking 
meat. It expels the natural fluids from the flesh fiber, 
and substitutes oil for these. When meat is cooked by 
frying, the fat should be heated very hot before the 
meat is put in, and it should be cooked rapidly, and 
removed as soon as it is tender. 

255. Cooking Vegetables. — Vegetables are usually 
cooked by boiling ; potatoes, however, are often prepared 
by baking ; and when it is carefully done, the result is 
very satisfactory. When vegetables are boiled, care 
must be taken that the process be not carried too far. 
As soon as the vegetable is soft it should be removed at 
once from the boiling water. If the cooking be con- 
tinued beyond this point, the structure will be broken 
down, and much of the vegetable will be dissolved in 
the water and lost. 

Potatoes, especially, should not be suffered to remain 
in the water a moment after boiling has ceased. While 
boiling, the pores of the vegetable are fil ed with steam, 



178 HYGIENE. 

but as soon as the temperature falls below the boiling 
point, the steam begins to condense, and the surround- 
ing water is drawn in to fill the vacuum, and the potato 
is water-soaked and indigestible. To a less extent, the 
*rame is true of beets, carrots, and parsnips. 

256. Bread — its importance as a diet. — The prep- 
aration of farinaceous food in the form of bread is at 
once the most difficult and the most important part 
of the culinary art. In civilized countries bread is a 
constant diet, a part of every meal ; and if it be badly 
made, unwholesome, and indigestible, the mischief will 
be in proportion to its universal use. 

The method of preparing bread by fermentation has 
undergone no material change since the ^ days of the 
oldest monuments of Egypt; and yet fermentation is 
not essential to the production of a wholesome and 
digestible bread. Indeed, fermentation is incipient 
decay, and all substances are less wholesome and nutri- 
tious after decomposition than before. So we find 
crackers, and kindred forms of unleavened bread, more 
digestible and nutritious than the ordinary form of fer- 
mented bread. In fermentation, flour loses all the 
sugar it originally contained, and this loss amounts 
to from six to ten per cent of the whole weight. 

257. Fermenting Bread — rules to be observed. — 

In making fermented bread, the chief secret lies in 
producing a rapid action ; and to secure . this, good, 
undamaged flour and fresh, active yeast must be used, 
with a temperature of about one hundred degrees 
steadily maintained. If fermentation begins slowly, 
or if it be arrested after it has commenced, either by 
too high or to r low a temperature, the first products 



MODE OF PBEPAKING FOOD. 179 

of fermentation will pass to the second stage, acetic 
acid will be formed, and the dough thus "soured will 
be spoiled. 

There is much more danger of fermentation going too 
far, and the bread being sour, than there is of arresting 
it at too early a stage by baking it. A very palatable 
and wholesome bread is made by forcing carbonic acid 
into the dough, under a high pressure, as it is being 
mixed. But this " aerated bread " can be produced 
only by expensive machinery, and therefore can not 
be made in common domestic establishments. 

258. The Qualities of Wholesome Bread. — By 

whatever method bread is produced, rapid and thor- 
ough baking is indispensable to a palatable and digest- 
ible article. The bread should not shrink on cooling, 
and there should be no clamminess on cutting a loaf. 
Several kinds of "baking powders" are in use to pro- 
duce spongy bread without fermentation. These consist 
of carbonates of soda or potash, mixed wdth some of the 
vegetable acids, or with phosphoric acid. The last is 
the least objectionable, as the salt resulting from the 
combination is comparatively harmless. 

Perhaps the best method to obtain carbonic acid, to 
lighten bread without fermentation, is to mix good bi- 
carbonate of soda with dry flour, and a weight of pure 
muriatic (chloro hyclric) acid equal to the socla, with 
the fluid used to moisten the mass. The gas will be set 
free, and nothing but common salt will be formed. 



Eecapitulation. 

Cooking renders food more easily digested and develops its 
flavor. Meat is cooked by boiling, roasting, baking, broiling, 



180 HYGIENE. 

and frying. There is one general rule for applying the heat, 
to be observed in all these methods. Danger of boiling veg- 
etables too long. They should be removed from the water 
while it is yet boiling. Importance of bread as an article of 
diet. Antiquity of fermented bread. Fermentation not neces- 
sary to wholesome bread. Aerated bread is a substitute for 
the fermented article. 



LESSON XXXII, 



AUXILIARY FOOD. 



259. Oils and Fats — their dietetic value. — The 

group of oils and fatty substances forms an important 
element in the diet of the inhabitants of cold climates. 
The animal' tissues containing fatty deposits are usually 
subjected to the same cooking processes as the fibrous 
meats, but the oil undergoes no change whatever in the 
operation. This class of food, however, is not confined 
to animal substances, bat is found extensively distrib- 
uted through the vegetable kingdom. 

Oil is the most concentrated form of heat-producing 
food; therefore most appetites demand it in cold weather, 
even in our temperate latitudes. Its rapid combination 
with the oxygen inhaled by the lungs is also an im- 
portant source of vital force, and it is on this account 
that persons engaged in severe labor in the open air 
demand oily food. 

260. Oily Food for Consumptives. — Of late it has 
been maintained that a deficiency of oily food pre 



AUXILIARY FOOD. 181 

disposes to consumption, and a careful observation 
of the early habits of consumptive persons shows that 
a very large proportion of this class were not in the 
habit of eating fat meats, many of them declining 
even butter. Dr. Carpenter says: "There is a strong 
tendency and increasing reason to believe that a defi- 
ciency of oleaginous matter, in a state fit for appro- 
priating by the nutritive processes, is a fertile source 
of diseased action, especially that of a tuberculous 
character; and that the habitual use of it in large 
proportions would operate favorably in the prevention 
of such maladies." 

It is, however, an unsettled question, whether this 
abstinence from fatty food is the cause or the effect of 
the consumptive tendency. Care should be taken that 
oils, fats, and butter used for food be fresh and sweet. 
Rancid fat or butter is always unwholesome. 

261. Salt — its use in the Animal Economy. — There 
are many substances which enter into our daily bill of 
fare which are not properly food, and yet they affect 
our health in a very important degree. Common salt 
(chloride of sodium) may with propriety be placed at 
the head of this list. It has been held by some writers 
that salt is not necessary to the maintenance of good 
health, and even that its use is injurious. 

It is true that many savage tribes, living almost 
exclusively on animal food, have maintained good 
health without the use of salt; but extensive ob- 
servation proves that persons living on a mixed diet, 
or chiefly on vegetables, lose their health when salt 
is withheld from their food. Both chlorine and sodium, 
the two elements of which salt is formed, are essential 



182 HYGIENE. 

to the digestion of food, the former furnishing the acid 
for the gastric fluid, and the latter the alkaline proper- 
ties of the bile. In flesh-eating tribes, these are fur- 
nished in sufficient quantity from the animal food on 
which they subsist. 

262. Salt retards Transformation. — Salt has an- 
other office in the animal economy. It appears to be 
a kind of governor, regulating the rate at which the 
changes in the body proceed. Salt is an antiseptic, 
and therefore retards the transformation cf the tissues. 
Lean persons of active habits have an instinct for 
salt, and generally use it freely with their food; 
while persons of full habit, or tending to corpulency, 
use it but sparingly, the transformation being already 
too slow. 

Pepper and other condiments, such as mustard, horse- 
radish, etc., are direct stimulants, both on the local 
surfaces with which they come in contact, and on the 
general circulation. By their local action they increase 
the flow of saliva and gastric fluid; but the quality of 
these secretions is impaired nearly in the proportion 
that their quantity is increased, so that really little or 
nothing is gained in the digestive process. 

263. Eifect of Highly-seasoned Food. — The con- 
tinued and habitual use of highly-seasoned food vitiates 
the secretions of the mouth and stomach, and thus 
impairs digestion; and worse even than this, such 
stimulants impair the sense of taste and pervert the 
appetite, the natural faculty of selection, and the power 
of determining both the quantity and quality of food 
which the necessities of the system demand. In a 
healthy condition, the digestive organs will not require 



AUXILIARY FOOD. 183 

condiments to assist them in the performance of 
their work. 

If this is true of pepper and kindred stimulants, 
it is more intensely important in regard to wine, beer, 
and other alcoholic drinks used at meals, under the 
pretext of creating an appetite. Such beverages not 
only act as a local irritant on the mucous membrane 
of the stomach, but the effect of the alcohol is to impair 
sensibility in the nerves of that organ, and to disturb 
if not suspend digestion by its well-known power of 
preserving organic substances from decomposition or 
change. 

264. Vinegar — its effect on Digestion. — Vinegar 
is extensively used as an auxiliary food. It furnishes 
no nutriment; indeed, it is not digestible; but when 
nitrogenous food is taken in large quantities, or in 
such form, as to be difficult of digestion, the secretion 
of the stomach frequently fails to furnish the acid 
quality of the gastric fluid sufficiently to complete di- 
gestion before putrefaction takes place. Vinegar more 
nearly supplies this defect than any other substance 
which could be used with safety. 

Nitrogenous vegetables, such as cabbage, etc., are 
rendered more digestible by vinegar. Two precautions, 
however, are necessary in the use of vinegar: 1st. We 
should be sure that it is vinegar that we are using, as 
many dangerous compounds of cheap mineral acids are 
sold for vinegar; 2d. The vinegar for the table should 
be largely diluted with water. 

265. Soda — its use in Cooking. — Much has been 
said of the use of soda in the different culinary proc- 
esses, and considerable alarm has been manifested ovei 

B. P.— 16. 



184 HYGIENE. 

the constantly increasing use of this article. While it 
admits of no doubt that caustic soda is a dangerous 
poison, and that even the milder carbonate is unfit to 
be taken into the stomach in that state, yet it must be 
remembered that, in cooking, the use of soda is confined 
almost exclusively to the neutralizing of acids which it 
is desirable to get clear of, or as a means of obtaining 
carbonic acid to lighten bread artificially. In either 
of these instances the soda becomes a neutral salt, and 
nearly all the salts of soda are harmless. 

But it may be well to say that, though no bad effects 
result from the use of well neutralized soda, yet the 
practice of using it to mitigate the acid of sour fruits, 
in cooking them, has the effect to impair their flavor 
and ultimately to render them insipid. 

266. The Appetite— when it is safe to follow it. — 

Before closing the subject of the quality of food as 
affecting health, it will be proper to state, in general 
terms, that the most reliable guide in selecting our 
bill of fare is an unperverted appetite. This, however, 
is very rarely to be found in civilized communities. 
The false and often pernicious theories of nurses and 
mothers too frequently establish wrong habits and 
perverted tastes, long before the unfortunate victim 
learns to form a proper judgment by his own reason- 
ing from physiological laws; and even then it too 
often happens that wrong habit is stronger than right 
knowledge. 

Children naturally prefer plain, simple, nutritious 
food, but if they are fed on that which is highly- 
seasoned and stimulating, accompanied with wine or 
other narcotic beverages, plain food will soon fail to 



QUANTITY OF FOOD. 185 

gratify their desires. The appetite is then an unsafe 
guide. 

Recapitulation. 

Oils and fats are demanded in cold climates, and in the 
winter season of temperate climates. Their necessity in the 
diet of those predisposed to consumption. Salt furnishes the 
chlorine and soda necessary for healthy action of the system. 
It retards transformation of the tissues. Highly-seasoned food 
and stimulating condiments are injurious. Vinegar hastens the 
digestion of nitrogenous food. Soda, when used in cooking, 
should always be neutralized by an acid. An unperverted 
appetite is the best guide in the selection of food. 



LESSON XXXIII. 

QUANTITY OF FOOD. 

267. Quantity of Food. — The quantity of food 
necessary to the maintenance of good health has been 
variously stated by different authors. Indeed, there 
are so many modifying circumstances connected with 
this question, that no definite statement can be made 
that will be in any degree reliable. Age, sex, tem- 
perament, occupation, state of health, and previously 
established habits, each exerts a greater or less influ- 
ence on the demands of the system for support. 

Dr. Dalton says that a man in full health, living on 
a diet exclusively of bread, butter, and meat, with coffee 
and water for drink, and exercising in the open air, 
will require, in each twenty-four hours, nineteen ounces 



186 HYGIENE. 

of bread, three and one-half ounces of butter, and six- 
teen ounces of meat, with fifty-two ounces of drink. 
The army rations of the United States soldier exceed 
Dalton's estimate by about twenty per cent, besides 
adding rice, sugar, and beans to the bill of fare. The 
rations in European armies are somewhat less than 
this. 

268. Digestion modifies Food. — The more or less 
perfect manner in which the digestive process is 
performed, is a modifying circumstance to which too 
little importance has been attached. Two persons, 
each in good health, of the same age, and following 
the same occupation, will eat equal quantities of the 
same kind of food, and yet derive nutriment from it 
in very different proportions. 

It is not the quantity of food taken, but the amount 
digested, which ministers to the support of the living 
body. This defective digestion may depend on a nat- 
ural debility, a lack of vital force in the organs con- 
cerned in the work ; but more frequently it is the result 
of bad habit, the habit of overeating, formed in early 
life. As the digestive process will seldom take from 
the food more nutriment than the demands of the 
system require, so when that amount is obtained the 
work is suspended, and the residue is passed off as 
waste matter. 

269. Use of Tobacco. — Persons addicted to the 
use of tobacco require a larger amount of food to 
furnish the same nutrition than persons who do not 
use the narcotic. The saliva, being rendered unfit 
for its office, is wasted, and the starchy part of the 
food, which should have been converted into sugar 



QUANTITY OF FOOD. 187 

by this fluid, remains to a great extent unchanged. 
The saliva is less important in the digestion of animal 
food, and for this reason those who use tobacco in- 
stinctively become largely flesh-eaters, or the habit 
induces dyspepsia. 

Alcoholic drinks produce similar effects, by impairing 
the sensibility of the stomach, and diminishing its vital 
force. By these derangements the stomach permits the 
imperfectly digested food to pass the pyloric orifice, and 
so but a small amount of its nutriment is made availa- 
ble. The appetite demands more food, and this morbid 
and pernicious effect of the " bitters" is often mistaken 
for an evidence of increased nutrition. 

270. Temperature — its influence on Food. — A few 

general principles, judiciously applied, will be found 
more effectual in regulating the quantity of food than 
any special rules that can be laid down. In childhood 
and youth, the nutrition must not only supply the 
waste of the system — which is greater in a given time 
than in adult age — but also a surplus, to be applied to 
growth. 

In cold weather the transformation of the tissues is 
more rapid, and a greater amount of heat-producing 
food is consumed to maintain the temperature of the 
body. The amount of this increase will be modified by 
circumstances. Persons well provided with warm cloth- 
ing, living in comfortable houses, and spending their 
time chiefly in well-warmed apartments, will scarcely 
require any increase of food; but the poorly clad and 
housed, and those engaged in out-door occupations, 
will require their food to be greatly augmented in 
cold weather. 



188 HYGIENE. 

271. Exercise and Ventilation vary the quantity 
of Food. — Active muscular exercise draws largely on 
the vital force; but the evolution of force is intimately 
connected with the wastes of the body, the oxidation 
of the food we digest, and of the worn-out particles of 
the body. These wastes must find an appropriate com- 
pensation in an increase of food. If the exercise be in 
the open air, the atmosphere pure, and the breathing 
free, the increased demand for food will be much greater 
than if the same exercise had been taken in a close', ill- 
ventilated room. 

But the force furnished to perform the exercise or 
labor will be in the exact proportion of the wastes to be 
supplied, and if the demand for food is not increased, 
the ability to perform the exercise will soon fail. From 
this cause persons are capable of performing more severe 
.and longer protracted labor in the open air than in 
badly-ventilated rooms. 

272. Change of Habits demands change in Food. — 

In altering their habits of life, persons should be care- 
ful to adapt the quantity of food to the modified condi- 
tion. If the change be from sedentary, in-door occupa- 
tion to active, open-air labor, the appetite will generally 
point out the proper alteration in diet; but changes in 
the opposite direction are not so promptly indicated, 
or, if so, the indications are not always heeded. 

Pupils leaving the active employments of the farm, 
and confining themselves to the school-room, often injure 
their health by continuing the same diet, both in quan- 
tity and quality, which they found necessary when 
engaged in daily labor. After a careful attention to 
this subject for the first week of school life, it may be 



QUANTITY OF FOOD. 189 

safely intrusted to the appetite. Persons making such 
a change of habits are frequently alarmed at their 
failing appetite, and resort to medicines to provoke 
a desire for food. This is all wrong. 

273. Mental Labor — the diet it demands. — Pupils 
at school, and other persons engaged in mental labor, 
need a plain, liberal diet. The amount of food devoted 
to muscular repair and the production of animal heat 
should be reduced proportionally to their diminished 
physical exercise, yet it by no means follows that it 
is necessary to starve the body to invigorate the mind. 
This hypothesis, so popular a few years ago, has been 
superseded by more rational views. 

Brain is exhausted by activity even more rapidly 
than muscle, and the waste of its material is propor- 
tionally great. To replace this wasted matter requires 
a full supply of food, rich in albumen and the phos- 
phates. Eggs, fish, oysters and other shell-fish, the 
lean part of mutton and beef, and wheat bread, are 
all articles rich in brain elements, and may be used, 
liberally if cooked plainly, with no other seasoning 
than salt. Fruits, either raw or cooked by stewing or 
baking, may be introduced as dessert. 

274. Bribing the Appetite. — The appetite is the 
only measure to determine the quantity of food to be 
taken, but many devices have been invented to bribe 
the appetite to take more food than the demands of 
the system require, or to take it when none is needed. 
Highly-seasoned food perverts the appetite, and renders 
it an unsafe guide. A great variety of dishes at the 
same meal has the same effect. 

A single course, consisting of one kind of meat or 



190 HYGIENE. 

eggs, one variety of vegetables, with bread and butter, 
and some palatable, unstimulating diet drink, in very- 
moderate quantities, will furnish a meal which may be 
supplemented by a dessert of fruit. Of such a repast, 
the appetite will determine very accurately when to 
desist from eating. A person should never suffer him- 
self to be decoyed into taking food when there is no 
desire for it. 

Recapitulation. 

The quantity of food demanded to supply the wastes of the 
system depends primarily on its perfect digestion. Tobacco 
and alcohol impair digestion. Temperature modifies the de- 
mand for food. A change of habits of life requires a corre- 
sponding variation in diet. Exercise and good ventilation in- 
crease the demand for food. Brain labor needs a generous 
diet. The use of highly-seasoned food renders the appetite 
an unsafe guide. 



LESSON xxxiy. 



TIME OF TAKING FOOD. 



275. Intervals at which Food should be taken.— 

Food should be taken at such intervals as will permit 
the stomach to perform the labor of digestion, and en- 
joy a period of rest about equal to the time of its 
active work. An ordinaiy meal, in a healthy stomach, 
will be disposed of in about three hours; and if we 
allow the same time for rest, this will make an inter- 
val of six hours between meals. 

Nearly all civilized nations have adopted the rule 



TIME OF TAKING FOOD. 191 

of three meals per clay — a few, more than this, and 
some, less. But individuals are found, in all commu- 
nities, who depart from the general usage of society in 
one direction or another. 

Whatever rule is adopted, it should be made a uni- 
form habit, which should not be violated except under 
the most urgent necessity. When a habit is fully 
established, the quantity of food will not depend on 
the number of meals. A person eating but once in 
twenty-four hours will take as much food at that one 
meal as he would take if it w r ere divided into three 
meals. 

276. Early Breakfast— why required.— When three 
meals are taken, the morning one should come early, 
or at least before we enter on any of the active duties 
of the day. The long interval between supper and 
breakfast is or should be an interval of rest, yet the 
active absorbents have carried into the circulation, in 
this time, all the nutritious matter derived from yester- 
day's food, and the stomach is now in an empty con- 
dition, awaiting a fresh supply. Any heavy drafts on 
the vital force in this condition can not fail to seriously 
disturb the equilibrium of that force, and derange im- 
portant functions. 

In this state, the system demands that the digestive 
apparatus should be early set at w T ork to prepare nutri- 
ment sufficient to meet the heavy drafts of a day of 
active exertion. This view of . the subject demands 
that breakfast should be a substantial meal of good, 
nutritious food. 

277. Dinner — its proper time. — Dinner should not 
be delayed much beyond six hours after the morning 

B. P.— 17. 



192 HYGIENE. 

meal. Late dinners require that the interval between 
them and the evening meal be too short, or that the 
latter be crowded too close to the hour of retiring for 
sleep. If the meals be taken at regular intervals of 
six hours, beginning at about seven o'clock in the 
morning, they may all be made full meals of sub- 
stantial food; but if the dinner be delayed till four 
o'clock in the afternoon, the evening meal, if not en- 
tirely dispensed with, should be very light both in 
quantity and quality, and should be taken not later 
than eight o'clock. 

Late suppers of heavy, indigestible food are a fruit- 
ful source of dyspepsia, and that long train of nervous 
diseases which render life an intolerable burden to so 
many. No food should be taken nearer than two 
hours to the time of retiring, and that time should not 
be later than ten o'clock. 

278. Eating between Meals — its pernicious effects. — 

The practice of eating "pieces" between meals is a 
most pernicious habit, and one that is the prolific 
cause to which may be traced the ruin of so many 
constitutions, even in childhood. When food is taken, 
a full meal should be made, and the stomach should 
then be permitted to digest it without disturbance. 
But if fresh portions of food be introduced when the 
stomach has half finished its work, the result is that 
neither portion is properly digested; for the process 
is thereby prolonged, the stomach is virtually kept at 
constant labor, and its powers are so enfeebled and 
exhausted that it fails to provide the means of nu- 
trition sufficient to supply the demands of the system, 
or to compensate for its daily waste. 



TIME OF TAKING FOOD. 193 

Loss of appetite and general debility ensue, followed 
by a train of nervous derangements that disturb all 
the vital functions. Half the ruined constitutions, 
that are not traceable to alcohol and tobacco, may 
safely be referred to the habit of eating between 
meals. 

279. Meals should not be interrupted. — Eating 
should be done slowly and deliberately, but it should 
also be done continuously. By this we mean that, 
when a meal is begun, it should proceed without 
any considerable interruption to its termination. The 
stomach does not begin the process of digestion till eat- 
ing is finished; but if, after the first course at a fashion- 
able dinner, there is an interval of ten minutes, a 
healthy stomach will go promptly to work on the food 
already taken. But this will be interrupted by the 
second course, and the stomach, thus disturbed, will re- 
turn to its task tardily, and will be likely to do its 
work imperfectly. 

Extremes of temperature in our food should be 
avoided. Food, to be promptly digested, must vary but 
a few degrees from blood-heat. Hot food and drink, or 
ice-water, ice-cream, etc., taken into the stomach, sus- 
pend all action till the mass has acquired the tempera- 
ture of the body. (§ 224.) 

280. Importance of thorough Mastication. — Good 
health depends not alone on what we eat, and when 
we eat it, but the manner of taking food is of the first 
importance in this relation. Eating, as we have said, 
should be done slowly and deliberately, and the masti- 
cation should be thorough. This is demanded more 
especially with regard to the starchy forms of food. 



194 HYGIENE. 

Saliva is the immediate agent by which starch is 
changed into sugar, and thus rendered soluble and 
transformed into available nutriment. 

But if the food be hurried through the mouth, and 
but imperfectly mixed with saliva, the digestion will 
be equally imperfect, and much of the nutriment lost. 
A worse defect in mastication than this occurs when, 
by the use of tobacco, the saliva is poisoned and ren- 
dered unfit for the purposes of mastication; or the 
salivary glands, goaded to constant overaction, secrete 
a fluid which contains none of the essential properties 
of saliva, and therefore can not aid in digestion. 

281. Good Teeth necessary to Mastication. — The 

grinding of food, the mechanical work of mastication, 
is performed by the teeth ; and in order that the work 
should be well done, the machinery should be kept in 
good order. But, in this country, a good, sound set of 
teeth, in a middle-aged person, is rare. Many things 
have, each in their turn, been charged with causing 
the premature decay of teeth, so common and so dam- 
aging to good health. 

It is pretty clear that the mischief is traceable to a 
combination of causes rather than to any one agent. 
The teeth are covered with an enamel which, if prop- 
erly taken care of, will protect them from the chemical 
action of any thing proper to be taken into the mouth; 
but this enamel may be broken, either by mechanical 
means, or by taking food too hot or too cold, and decay 
will inevitably follow. 

282. Rnles for preserving the Teeth. — The pres- 
ervation of the teeth is a subject of too much impor- 
tance to be passed over lightly; we therefore submit a 



TIME OF TAKING FOOD. 195 

few general rules for their care. After eating, the teeth 
should be thoroughly cleaned, removing, by means of a 
tooth-pick of wood, quill, or ivory, whatever has lodged 

between them, and washing the mouth with tepid water. 
Never use a metallic instrument of any kind to clean 
the teeth, for in its use there is always a liability to 
fracture the enamel, which is, of all things, most to be 
guarded against. 

All tooth-powders and dentifrices are to be avoided, 
for even the constant rubbing of the teeth with pow- 
dered charcoal will ultimately wear through the enamel, 
and expose the teeth to decay. A soft brush, a little 
fine soap, and soft water about blood-heat, will cleanse 
the teeth more thoroughly and more safely than the 
most expensive dentifrice. 

Recapitulation. 

Three meals a day generally adopted in civilized countries. 
Meals should be taken at intervals of at least six hours. 
Breakfast should be eaten before commencing the day's labor. 
Late dinners bring the evening repast too near the hour of 
retiring. The pernicious effects of late suppers. Eating be- 
tween meals is a fruitful source of indigestion. The digestive 
apparatus must have time to rest. Meals, when once begun, 
should not be interrupted. Care of the teeth important to 
good health. 



196 HYGIENE. 

LESSON XXXV. 

CONDITION OF THE SYSTEM. 

283. Do not eat when fatigued. — The condition 
of the system, at the time of taking and digesting 
food, is a matter not to be overlooked in the hygiene 
of nutrition. To digest a full meal, is an operation 
which draws heavily on the nervous system for the 
force necessary to maintain the constant motion of 
the stomach, by which its contents are moved about 
so that every part of it may be brought in contact 
with the surface secreting the gastric fluid, as well 
as to keep up a full flow of this secretion. 

Now if labor of muscle or mind has been carried to 
fatigue, and a feeling of exhaustion is experienced, it 
would be very improper to take food until the ex- 
hausted vital force has been restored by rest. Persons 
engaged in active labor, or in hard study, should allow 
themselves at least half an hour for rest of body and 
mind before assigning to the stomach its task of digest- 
ing a meal. 

284. Rest should follow Meals. — It is equally im- 
portant that an interval of rest and relaxation should 
follow each meal. The action of the stomach is invol- 
untary, and proceeds without our knowledge or con- 
sent; yet, if a strong effort be made to carry on any 
voluntary function, the vital force will be directed to 
the organs concerned in that work, and being thus 
turned away from the stomach the work of digestion 
can not proceed for want of power. 



CONDITION OF THE SYSTEM. 107 

It is not merely vigorous muscular exertion which 
produces this effect, but it may be even more certainly 
induced by brain labor. Some of the most inveterate 
cases of indigestion are traceable to the habit of spend- 
ing the dinner hour in reading and hard study. This 
is a habit which laboring men, anxious both to acquire 
knowledge and economize time, are apt to fall into, and 
against which they should be warned. 

285. Cheerfulness during Meals. — A lively, cheerful 
state of mind, as far as this can be commanded, should 
accompany all our meals; and if the surrounding 
circumstances force on us the melancholy mood, our 
meals should consist of light, digestible food, in small 
quantities. Under such circumstances the appetite 
will seldom demand food; and care must be taken 
that we are not decoyed into the mistake of attempt- 
ing to create an appetite by local stimulants, or of 
escaping from the cares that oppress us by a resort 
to alcoholic exhilarants. 

At least half an hour should be spent in sprightly 
conversation or amusement after a meal is taken. 
Light reading, which will amuse and entertain, w T ill 
furnish a safe means of passing this interval between 
eating and business. But works of fiction which appeal 
strongly to the imagination or rouse emotions should 
be carefully avoided. 

286. Rest after Meals — objection to the Siesta.— 

The half hour of rest after meals, which we have 
recommended, will be sufficient, in most persons, to 
start the process of digestion; and when the stomach 
has become fully engaged in its work, it w r ill not be 
easily diverted from it. But on resuming business 



198 HYGIENE. 

we should begin moderately, and not tax our powers 
to their full capacity for at least the first hour of 
labor. When the time can be spared, it will be 
safer to lengthen the period of rest after eating to 
an hour, which could be economized by devoting it 
to some easy task that will but lightly tax either 
muscle or brain. 

To the Spanish siesta, or hour of sleep after dinner, 
there is a physiological objection. All the vital powers 
are depressed during sleep, and the stomach feels this 
lowering of vital force in common with all the other 
organs, and consequently digestion can not be perfectly 
performed. 

287. Food not to be taken when there is no Appe- 
tite. — We have, in a previous lesson, intimated that 
food should be taken at regular intervals, and this 
regularity should be maintained till it grows into a 
habit. This, however, is to be accepted under certain 
restrictions. There are conditions of the system in 
which the appetite does not ask for food, and in 
which to take food into the stomach would only add 
a new source of irritation, which might, with existing 
disturbances, prove a cause of serious sickness. 

These conditions may be reduced to two general 
divisions, to witj Those in which the loss of appetite 
springs from derangements in the digestive apparatus, 
so that food, if taken, could not be properly digested, 
and, by becoming either acid or putrid in the stomach, 
would not fail to seriously irritate that organ; and 
those in which the loss of appetite arises from dimin- 
ished wastes of the system, reducing the demand for 
nutrition. 



CONDITION OF THE SYSTEM. 199 

288. Abstinence— when necessary. — The first of 
these conditions, resulting in a loss of appetite, usually 
has its origin in improper eating as to the quantity 
of food, its quality, or the time of taking it. Under 
these circumstances nothing more is necessary than 
to abstain from eating and await a return of appetite. 
If there be no serious disease approaching, abstinenco 
from food for twenty-four hours will correct the dis- 
turbance and bring a renewed appetite. 

The second condition may generally be traced to a 
lack of active exercise in the open air. When the 
change or transformation of the tissues is retarded, 
the demand for new material is proportionally dimin- 
ished, and the digestive organs refuse to prepare nutri- 
tion beyond the healthy demands of the system. 

289. Efforts to create an Appetite. — The habit 
of urging food on invalids when there is no desire 
for it, is only equaled in absurdity by the opposite 
error of denying food to convalescent persons when 
the appetite imperiously demands it. In these con- 
ditions of the system, which disqualify the digestive 
apparatus for the performance of its proper office, it 
is a very grave mistake to resort to medicines to create 
an artificial appetite. 

When we look at the formidable catalogue of tonics, 
and bitters, and other nostrums, with which the public 
regularly doses itself, and all for the purpose of provok- 
ing an appetite against the wiser instincts of the sys- 
tem, it is surprising that comparatively so little mis- 
chief is done by all this war on nature. Out of this 
injudicious tampering with the digestive organs grow 
most of the chronic diseases, which make so many 



200 HYGIENE. 

invalids, and induce premature old age in so many 

cases. 

290. Habits measure the quantity of Food.— The 
condition of the system, with regard to activity or 
rest, must modify our diet both as to quantity and 
kind; and it will be wise to depart even from the 
general rule of following the appetite when changes 
in manner of life are suddenly made, especially if the 
change be from active labor to absolute rest. Under 
these circumstances, it will be prudent to leave the 
table while there is still a desire for more food. 

The changes of the season demand a corresponding 
change in our bill of fare. Oils and animal flesh may 
be taken freely in winter, if we follow out-door occupa- 
tions, but when the relaxing days of spring come, we 
should keep lent, for health, if from no other motive. 
Never take food late at night when the system is 
oppressed with a feeling of drowsiness or languor. 

Recapitulation, 

Food should not be taken when there is fatigue of either 
muscle or brain. Meals should be followed by rest. Cheerful- 
ness and mental relaxation at meals are important. Sleep 
should not be indulged in during digestion. Food is not to be 
taken when there is no desire for it. Abstinence from food — 
when proper, and to what extent. Efforts to create an arti- 
ficial appetite are injurious. Change of habits or of season 
demand a corresponding change of diet. 



CIRCULATION. 201 

LESSON XXXVI. 

CIRCULATION. 

291. Sympathetic Relations of the Heart and Blood- 
vessels.— The circulatory apparatus has an extensive 
range of sympathies, being affected, more or less, by 
every change which takes place in any of the impor- 
tant organs of the body; but the circulation is subject 
to fewer direct disturbances than any other function 
of the living body. 

The heart, the central organ of the circulation, is so 
situated that it is removed from liability to injury by 
external accidents; and being an involuntary organ, 
the will exerts no direct control over it, and therefore 
it is not, like the stomach, liable to be overworked for 
any present gratification, or neglected in the hurry and 
press of other business. Nearly all the diseases to 
which the heart and blood-vessels are subject, have 
their origin in their sympathetic action with the 
digestive or respiratory functions, or with the brain 
and nervous system. 

292. Pressure on the Veins. — The veins perform 
the work of returning the blood to the heart, and 
are therefore an important link in the process of 
circulation. These are largely distributed on the su- 
perficial parts of the body, and are therefore peculiarly 
subject to external influences, such as change of tem- 
perature, mechanical pressure, etc. Moreover the veins, 
unlike the arteries, have soft and yielding coats, af- 
fected by the lightest pressure; and as the current of 
blood flowing through them is not impelled by any 



202 HYGIENE. 

direct active force behind it, therefore it is more liable 
to disturbances from external causes. 

If the clothing is so tight as to produce any sensible 
pressure, it will retard the return of venous blood, and 
will to that extent disturb the circulation. Tight gar- 
ters are a fruitful source of cold feet, which so many 
complain of. The return of blood from the feet being 
interrupted, the supply will be diminished in propor- 
tion. 

293, Compression of the Jugular Teins. — A more 
dangerous compression of the venous circulation is that 
occasioned by tight collars or neckties. The jugular 
veins, which return the blood from the head, are 
situated immediately under the skin, on each side of 
the neck, and are therefore very liable to compression 
from dressing the neck tightly. Compression of these 
vessels produces engorgement of the whole vascular 
system of the brain, manifesting itself by dizziness, 
a sense of fullness in the head, or severe headache. 

This will derange the mental machinery, and disturb 
all the functions of the nervous system. If the com- 
pression is considerable, and any active exertion is 
attempted, the engorgement of the brain is liable to 
terminate in apoplexy; but if the compression be 
moderate and long continued, the consequence will be 
that less blood will be sent to the brain, and the whole 
nervous system will be correspondingly weakened. 

294. Muscular Exercise and the Circulation. — But 

the circulation is affected indirectly by nearly all the 
activities of the body. Every contraction of a muscle 
makes momentary pressure on the veins in contact 
with it, and thus their contents are forced forward 



CIRCULATION. 203 

ill the direction of the heart, the valves preventing 
the flow in the opposite direction. The relaxtion of 
the muscle permits the veins to fill again, and thus 
the action of the muscular system increases the 
quantity of blood returned to the heart in a given 
time. 

This demands a more vigorous action of the heart, 
and, under this influence, the pulse becomes fuller, 
stronger, and more frequent. This increase of circu- 
lation by exercise is a healthy action, and with it an 
increased respiration is demanded for the full supply of 
oxygen, in order to break down and render soluble the 
old material of the tissues, that it may be removed by 
the absorbents. 

295. Changes of Temperature. — The temperature 
of the body and the circulation of the blood mutually 
affect each other. Whatever excites the circulation, 
and induces a greater transmission of blood through 
the capillaries, increases the temperature in the same 
proportion ; and, on the other hand, if any part of the 
body be exposed to a very low temperature, the vessels 
will be contracted, and the circulation in that part 
diminished. 

This may be general, as in a cold bath ; or local, as in 
the application of ice to any part of the body. But 
when there is a depression of the circulation from 
sudden exposure to cold, there is always an effort of the 
system to overcome the obstruction by augmenting the 
force of the circulating current. Under these circum- 
stances, if the depressing cause be removed, the tem- 
perature suddenly restores itself and even rises above 
its former standard; and the increased action of the 



204 HYGIENE. 

capillary circulation will be maintained for several 
hours. 

296. Change from Cold to Heat, most dangerous. — 

But in feeble health this reaction does not always take 
place, especially if the low temperature be long en- 
dured. Persons, therefore, of feeble vitality should be 
cautious in exposing themselves to a low temperature, 
whether in the bath, or in a cold atmosphere ; and they 
should bear in mind that the reactive force diminishes 
with the length of the exposure. 

The increased force of the circulation, whether from a 
high temperature of the surrounding medium, or from 
violent and long-continued exertion, is more to be 
dreaded as a cause of disease than exposure to a low 
temperature. Changes of weather from cold to warm 
are more unfavorable to health than those in the oppo- 
site direction. By the increased vascular action there is 
induced a tendency to inflammatory diseases. 

297. Influence of the Mind on the Circulation. — 

The action of the heart is readily influenced by the 
mental condition. A powerful exertion of the purely 
intellectual faculties, as in the solution of some in- 
tricate problem, reduces both the force and fullness of 
the circulation, while the action of the heart becomes 
more frequent, and often irregular, 

Anger and the other exciting passions increase the 
force of the heart's action sometimes to an alarming 
extent. The depressing passions, such as sorrow or 
grief, render the pulse empty, slow, and feeble. Under 
the influence of these depressing passions, the power 
to resist disease is greatly diminished, as was demon- 
strated when cholera visited our cities a few years since. 



CIRCULATION. 205 

The condition of the circulation is the best measure 
of the vital force which is in our reach. A heart-action 
which maintains its uniformity, and is but little dis- 
turbed by the various exciting causes, indicates a 
powerful life force which will resist all ordinary causes 
of disease, and restore health under circumstances that, 
with a feeble circulation, w T ould be hopeless. 

298. Bleeding from Arteries or Veins. — Though 
the heart and larger arteries are well secured from 
injury by ordinary accidents, yet the superficial vessels 
are often injured, and it is frequently of the first impor- 
tance to be able to distinguish the bleeding of an artery 
from that of a vein, as this discrimination will decide 
what must be done. (§ 48.) 

When an artery is divided, the bleeding can be 
arrested only by tying the vessel; but the immediate 
danger can generally be met by compressing the vessel 
above the wound, or on the side next to the heart, till 
a surgeon is obtained. 

Recapitulation. 

The circulatory organs are in sympathy with all the func- 
tions of the body. Danger from compression of the veins by 
tight clothing. Nearly all the activities of the body affect the 
circulation indirectly. Temperature and circulation mutually 
influence each other. Reaction from exposure to cold — neces- 
sary precautions. Mental exercise and the influence of the 
passions affect the circulation. 



206 HYGIENE. 

LESSON XXXVII. 

BREATHING. 

299. Breathing — its complex character. — The 

organs concerned in respiration are intimately con- 
nected with a long train of dangers to health, both 
from the defective performance of their functions, and 
from the unwholesome condition of the air used in 
breathing. Foremost among these dangers stand prom- 
inent the restrictions on the respiratory movements 
from improper dressing. 

We have already described (Lesson VII) the process 
of breathing as being carried on jointly by the dia- 
phragm, the muscles between the ribs (intercostals), 
and the muscles forming the front part of the abdomen. 
Now, breathing may be imperfectly carried on by the 
diaphragm alone, but perfect breathing requires the 
joint action of all these organs, operating without 
restraint and with the utmost freedom. But our 
modern style of dress defeats this end so completely, 
that we rarely see a person breathing naturally. 

300. Movement of the Ribs in Breathing. — Much 

that has been written on the subject of tight lacing has 
been misunderstood, or the statements have been so 
indefinitely made that they have rather served to mis- 
lead than to instruct those for whose benefit they were 
written. 

The motion of the ribs in expanding the chest in- 
creases as we descend in the series. The first rib is a 
fixed point, and the second one is moved upward a 
given amount ; the third moves twice as much as the 



BKEATHING. 207 

second, the fourth three times as much, and so on 
through the whole series, so that the twelfth rib should 
have eleven times as much motion as the second one. 
At a glance it will be seen how much more injurious 
it is to compress the lower than the upper part of the 
chest, yet our modern styles nearly relieve the true 
ribs, and put all the compression on the false and 
floating ribs. 

301. Injurious effect of Compression. — But the 

compression of the chest is not the only thing to be 
guarded against in this relation. In healthy breathing 
there is a free motion of the abdominal muscles, and 
if this motion be in any way interfered with, the 
breathing will be imperfect. 

To suspend the lower garments by a band passed 
around the loins, will prevent all free motion of the 
muscles on the front and sides of the abdomen, and 
to that extent impede respiration. And this remark 
applies not merely to women's clothing; the habits 
of dress common among men confine the abdomen 
by too tight a waistband, so as to materially interfere 
with the freedom of breathing. The lower garments, 
whether in male or female dress, should be suspended 
from the shoulders, so as to leave the most perfect 
freedom of motion to the lower part of the chest and 
abdomen. Compression need not be violent in order 
to be injurious. A very moderate pressure, constantly 
kept up, will be sufficient. 

302. Compression — when most injurious. — Im- 
proper clothing is much more injurious to young per- 
sons than to those of mature age. In youth the car- 
tilages are soft and yielding; a compression, therefore, 

B. P.— 18. 



208 HYGIENE. 

which in older persons would hardly be felt, will in a 
short time produce permanent distortion of the ribs, 
and entail on the unfortunate and, perhaps, unconscious 
subject of it, a feeble vitality, which will constantly 
invite all the ailments that flesh is heir to. 

Mothers, in the dressing of their children, have a 
great responsibility resting on them. We can not be 
too often reminded that vital force is measured by 
the amount of chemical change going on in the body, 
and that these changes are limited, at least on one side, 
by the supply of oxygen furnished by the respiratory 
process. Free breathing is therefore a prime condition 
of vigorous health. 

303. Too frequent Breathing. — To one who under- 
stands the mechanism of breathing, it is an instructive 
lesson to watch the respiration of a company quietly 
seated in a room. Not one in ten breathes correctly. 
Many persons breathe with the diaphragm alone; 
others use the upper part of the chest almost exclu- 
sively; and but few bring into requisition all the 
means of inflating the lungs. 

This imperfect filling of the air-cells compels the 
breathing to be more frequent, in order to supply in 
some degree the deficiency of fullness. But this in- 
creased frequency not only exhausts the few muscles on 
which the whole labor is imposed, but the air is not re- 
tained in the pulmonary cells long enough to impart 
its oxygen fully to the blood, and receive, in turn, its 
charge of carbonic acid from it. A healthy person with 
well-developed lungs, breathing quietly, will fill them 
about fifteen times per minute; but persons, from a 
bad habit of breathing, or from ill-developed or com- 



BREATHING. 209 

pressed lungs, frequently respire twenty or twenty-five 
times per minute. 

904. Exorcise of the Vocal apparatus. — A free 
exercise of the lungs in singing, declaiming, or reading 
aloud, with careful attention to the method of breathing, 
is the best means of correcting, vicious habits in the 
use of the lungs and their associated apparatus. In 
these exercises, care must be taken that the diaphragm, 
ribs, and abdominal muscles are all brought into use 
and act in concert. 

Many public speakers and singers, when they suffer 
somewhat from embarrassment, are in the habit of 
rigidly contracting the abdominal muscles, and holding 
them firmly in that attitude during the whole perform- 
ance. This compels more frequent breathing than is 
convenient, deprives the voice of volume and force, 
and gives it the appearance of coming from the upper 
part of the throat only. Much of the throat disease in 
public speakers may be traced directly to this vicious 
habit of breathing. 

305. Imperfect Breathing, source of Feeble 
Health. — Imperfect breathing, from whatever cause 
it may arise, is more to be dreaded as inducing feeble 
health than almost any other cause, for the reason that 
it is seldom suspected either by those who suffer or by 
their friends. Though a compressed chest and unde- 
veloped lungs, with a bad habit of breathing, may not 
immediately lead to any actual disease, yet the dimin- 
ished vital force, which is an inevitable result of 
breathing imperfectly, will greatly impair the powers 
of endurance — the ability to sustain protracted efforts 
either of muscle or mind. 



210 HYGIENE. 

With this diminished vital force comes the enfeebled 
power to resist the encroachment of disease, or to restore 
the healthy action of the system after disease has super- 
vened. The chances of recovery from sickness are al- 
ways augmented by a well-developed respiratory ap- 
paratus and a good habit of breathing. Much of the 
feeble health that is complained of in this country, 
especially among women, is traceable to imperfect 
breathing as its remote cause. 

306. Breathing directly connected with Life.— 

Eating, drinking, sleeping, and exercising are condi- 
tions of life and health, }^et they are only remotely so; 
but breathing is an immediate and indispensable con- 
dition on which life depends directly; it is therefore 
the most important of all the voluntary functions we 
perform. Indeed, respiration is so immediately con- 
nected with life, that beyond a certain point of volun- 
tary control, the Creator has wisely removed it from 
our personal management, and placed it among the 
involuntary functions. 

In this view T of its importance, it is surprising to 
observe how little attention is usually paid to the 
whole matter of respiration, both with regard to how 
we breathe and what we breathe. Persons are often 
very particular to have their food scrupulously clean, 
but will not hesitate to breathe the air of a crowded, 
ill-ventilated hall, or to inhale volumes of second-hand 
tobacco smoke. 

Recapitulation. 

Breathing is a complex function, carried on by the joint 
action of several organs. Compression of the lower ribs is more 
injurious than that of the upper ones. Bad effects of com- 



PUEE A IK. 211 

pression on the abdominal muscles. Tight clothing is most 
injurious to the young. Too frequent breathing defeats the 
object of respiration. Use of the vocal organs as a means of 
correcting bad habits of breathing. Imperfect breathing is a 
source of feeble health. 



LESSON XXXVIII. 

PURE AIR. 

307. Composition of the Atmosphere. — A healthy 
respiration demands that pure air be supplied to the 
lungs at appropriate intervals and in proper quantities. 
This question of pure air is the more difficult to solve 
because many of the most objectionable impurities give 
to our senses no evidence of their presence. The atmos- 
phere consists of seventy-nine parts of nitrogen and 
twenty-one parts of oxygen. These are not chemically 
combined, but in a state of intimate mixture; or, 
more properly, the nitrogen acts as a solvent, and 
the oxygen is held in solution in it. This accounts 
for its uniformity in every place where it has been 
examined. 

Besides these two gases, the atmosphere holds a vari- 
able quantity of watery vapor, carbonic acid, ammonia, 
and other volatile substances, which it receives from a 
thousand sources. These impurities, however, where 
the air is allowed a free circulation, seldom exceed one 
part in a thousand. It is only where the air is confined 
that they accumulate so as to be dangerous to those 
who breathe them. 



212 HYGIENE. 

308. Natural means of Purifying the Air. — One 

of the most beautiful economies in nature is that by 
which the air is purified of the pollutions that are 
constantly poured into it from the breathing of ani- 
mals, the burning of fires, the decomposition of vegeta- 
ble and animal matter, etc. Like a great ocean, the air 
receives from all these sources constant streams of car- 
bonic acid and ammonia, which, if there were no coun- 
teracting agency, would soon render it utterly unfit to 
be breathed. But these noxious impurities are readily 
dissolved in water, and the showers, as they fall from 
the clouds, wash the air and purify it. 

To assist this process, the vegetable world spreads its 
broad, leafy surface to the breeze, where myriads of 
mouths on every leaf are open to drink up the carbonic 
acid from the air, and appropriate it to their own use. 
In this same leaf the impurity is decomposed, and its 
oxygen returned to the air to supply the constant waste 
of it by animals. 

309. Sources of Impure Air. — The influence of 
growing vegetation in purifying the air suggests the 
importance of trees and shrubbery about our dwellings, 
and of lawns and parks in the vicinity of large cities, 
where they will serve as reservoirs of pure air. What 
we are able to do, locally, to purify the air for our use, 
may be but a small matter, but much may be gained 
for health by carefully shunning the sourees of impure 
air. Ponds of stagnant water, marshes, and other accu- 
mulations of decomposing vegetable and animal matter, 
should be studiously avoided. 

Large assemblies in imperfectly ventilated rooms are 
most fruitful sources of mischief to the health of those 



PIKE AIR. 213 

who visit them. Air that has been once breathed is 
unfit for use until it has mingled with the great atmos- 
pheric ocean, and its original composition has been 
restored. By a wise provision, to prevent re-inhaling 
our own breath, it is rarefied by heat, and caused 
to rise above our heads as soon as exhaled from the 
lungs. 

310. Oxygen — its diminution by Breathing. — It 

has been ascertained by careful experiment that air 
exhaled from healthy lungs has lost about one-fourth 
of the oxygen it originally contained, and that the 
volume has been maintained by the substitution of 
carbonic acid for the oxygen abstracted. Some might 
infer from this that breathing the same air four times 
would rob it of all its oxygen. This is not the case. 
Air that has lost one-fourth of its oxygen by a first 
inhalation, will lose less than one-eighth the second 
time it is inhaled; and when the oxygen has been 
diminished one-half the original quantity, the air will 
no longer support life. 

On the other hand, the capacity of air to dissolve 
carbonic acid diminishes in a rapid ratio by the amount 
dissolved. Now, when we bear in mind that breathing 
performs the double function of supplying oxygen to 
the blood and removing carbonic acid from it, we shall 
perceive the importance of having the first use of all 
the air we breathe. 

311. Importance of thorough Ventilation. — The 

proper ventilation of rooms is a subject involving more 
of health and comfort than has been generally appre- 
hended. Public halls, churches, school-rooms, private 
apartments, and especially sleeping-rooms, should at all 



214 HYGIENE. 

times have a free supply of pure, fresh air, and a con- 
stant removal of that which has been vitiated by 
breathing. 

It is not necessary that air should be cold in order 
to be pure. Air may be warmed to any desirable 
temperature by a proper apparatus, and yet retain its 
healthy proportions unchanged. The only advantage 
in breathing cold air is, that heat expands air largely, 
and consequently a given volume of cold air contains 
more oxygen than the same volume of heated air. In 
w T arming apartments by a supply of heated air, we 
must guard against passing the air over red-hot surfaces 
of iron, as a portion of its oxygen will combine with 
the iron, and thus the amount available for breathing 
will be diminished in the same proportion. 

312. Care necessary in Warming Rooms. — When 
stoves or furnaces are used for the purpose of heating 
apartments, great care must be taken that the gases 
resulting from combustion of the fuel do not escape 
into the air being warmed by it. Dr. Nichols, of 
Boston, has demonstrated, by a series of careful experi- 
ments, that cast-iron, when highly heated, will permit 
carbonic oxide to pass through its pores, and render 
the air thus heated unsafe. 

An open grate or wood fire with a strong draft, 
though not a very good method of economizing heat, 
is an excellent ventilator and a safe way of warming 
small rooms; but when large halls or suites of rooms 
require heating, currents of warm air should be con- 
stantly introduced, which will demand that means be 
provided for the discharge of a corresponding current 
of vitiated air. This warm air should be supplied 



PURE AIR. 215 

either from a wrought-iron furnace or from a chamber 
heated by coils of steam or hot water pipes. 

313. Bad effects of ill-ventilated School-rooms.— 

In large manufacturing establishments, where un- 
healthy gases are generated, provisions should be made 
for carrying these away, by means of a high venti- 
lating stack, in which a rapid current is made to 
ascend constantly by the aid of proper machinery, 
thus effecting a thorough renovation of the air. 

The imperfect ventilation of school-rooms is an evil 
whose consequences can hardly be measured; and they 
are the more to be dreaded because their effects are of 
such a character as seldom to occasion immediate alarm. 
The direct consequence of breathing air containing 
a mixture of carbonic acid below the point producing 
a sense of suffocation, is to oppress the brain w f ith a 
feeling of languor and dullness, followed by an almost 
irresistible tendency to sleep. In this condition neither 
teachers nor pupils are fit for duty. In a room twenty- 
five feet square, fifty pupils w T ill breathe all the air it 
contains in a little more than two hours. After the 
first hour, the time spent in such a school-room is worse 
than wasted. 

314. Alcohol and Tobacco— influence on Respira- 
tion. — It is important, in the relation of acquiring and 
maintaining vigorous health, that the lungs be pre- 
served in such a state that the air will freely enter the 
whole of each lung, and that the air-cells be in such a 
condition that the oxygen from the air, and the car- 
bonic acid and watery vapor from the blood, may be 
freely transmitted through the walls of the cells. 

It is a familiar fact, that when spirituous liquors are 
B. P.— 19. 



216 HYGIENE. 

taken into the stomach, the alcohol begins directly to 
pass off by the lungs, and may be detected in the 
breath. But so delicate a membrane as that of the 
air-cells can not be subjected to the action of alcohol 
without serious injury. The same may be said of in- 
haling an atmosphere foul with tobacco smoke. The 
narcotic effect of tobacco smoke in its second use is 
worse than the first use of the fumes, as in that in- 
stance the poison is carried to the lungs, instead of 
merely affecting the mucous membrane of the mouth. 

Recapitulation, 

Healthy respiration requires pure air in proper quantities. 
Decaying animal and vegetable matters vitiate the air. Eain 
and growing vegetation are means of purifying the air. Large 
assemblies corrupt it. Air once breathed is unfit for use till it 
is purified. In exhaled air, 'the oxygen is reduced and car- 
bonic acid increased. Ill ventilation affects brain functions. 
Narcotics diminish the quantity of oxygen retained from the 
air inhaled. 



LESSON XXXIX. 

ANIMAL HEAT. 

315. Uniform Temperature of the Body.— Animal 
heat, being so intimately connected with the respira- 
tory function, will be appropriately considered in this 
place. The temperature of a healthy adult is about 
ninety-eight degrees; in infancy it is a little greater, 
and in old age somewhat less. It is astonishing to 
observe with what regularity the general temperature 



ANIMAL HEAT, 217 

is maintained in all climates, and under extreme 4 vicis- 
situdes of season. When persons are exposed in ex- 
tremely cold weather, the temperature of the extremi- 
and of the exposed parts of the face often sinks to 
near the freezing point; but, even at this time, a 
delicate thermometer, placed in the arm-pit or under 
the tongue, will show little or no variation from the 
uniform standard of ninety-eight degrees. 

Dr. Kane, in his Arctic explorations, was often ex- 
posed for hours to a temperature between sixty and 
seventy degrees below r zero, without materially affecting 
the heat of his body; and in a number of well-authen- 
ticated cases, persons have subjected themselves for 
hours to a temperature above the boiling point of 
water, and still the thermometer under the tongue 
marked ninety-eight degrees. 

316. Evaporation and Temperature. — These aston- 
ishing results can be explained only by understanding 
the relations existing between the pulmonary and 
cutaneous surfaces of the body. If the proper amount 
and kind of food be taken and digested, the tempera- 
ture will be measured by the quantity of oxygen re- 
ceived through the lungs in respiration; but the 
evaporation of water is a cooling process, and reduces 
temperature in proportion to its rapidity. 

The rapidity of evaporation depends, to a very great 
extent, on the temperature of the air. In a low tem- 
perature, the evaporation from the surface of the body 
is virtually suspended, and the heat evolved in the 
system is retained only as it is conducted away by 
exposure of the surface to the cold air. When the body 
is exposed to the other extreme of temperature, the 



218 HYGIENE. 

evaporation of perspiration from the surface is suffi- 
cient to keep the temperature down to ninety-eight 
degrees. 

317. Conditions of a uniform Temperature. — The 

power to maintain this constant equilibrium of tem- 
perature depends directly on the healthy action of the 
pulmonary surface — that is, the inner surface of the air- 
cells; and on the external, or perspiratory surface — the 
skin; and indirectly, on the supply of oily, starchy, or 
saccharine food, and the perfect digestion of the same. 
The failure of either of these conditions will be followed 
by a corresponding disturbance in the power to main- 
tain an equal temperature under changes in the heat 
of the atmosphere. 

In cold weather, the first condition of security 
against suffering is full and free breathing of pure 
air into healthy lungs. Many persons, on leaving a 
warm room and going into a cold atmosphere, feel a 
sense of chilliness, which induces a short, shallow 
breathing, as though they feared to fill the lungs 
with cold air. A few full inspirations will relieve 
this chilly sensation and restore a feeling of comfort- 
able heat. 

318. Precautions against a Cold Atmosphere. — But 

if there is an inability to fill the lungs, whether from 
temporary disturbance or from permanent disease, care 
must be observed in making sudden transitions from a 
warm to a cold atmosphere. Persons who have natu- 
rally small lungs, or who dress so that the larger part 
of the pulmonary surface is rendered useless, or those 
who, from present or previous disease, have the full 
use of only a small part of the breathing apparatus, 



ANIMAL HEAT. 219 

generate heat feebly, and should not be exposed to 
low temperatures. But even if the lungs supply a 
full amount of oxygen, the stomach may not have 
furnished the supply of combustible material with 
which this is to unite; there will then be a corre- 
sponding inability to maintain the temperature on 
exposure to cold. 

319. Overheated Rooms — ill effects. — Dyspeptics, 
and those who are suffering from pulmonary disease, 
or have a predisposition to it, while they are careful 
to avoid sudden transitions from one extreme of tem- 
perature to another, should be equally careful to guard 
against the too common error of constantly living in 
overheated rooms. 

Let invalids remember that the chemical action which 
goes on between the air we breathe and the food we 
digest is not only the source of animal heat, but of 
vital force. That uncomprehended, and perhaps incom- 
prehensible power also, by which all the movements of 
the living machinery are performed, is more or less 
directly connected with the same chemical changes; 
and whatever diminishes the amount of these changes, 
impairs the life-force in the same ratio. In a room 
heated to near the natural temperature of the body, 
there is but little demand for food, because there is 
very little chemical change required to supply the 
small deficiency of heat; but the vital force is also 
diminished in like proportion. 

320. Proper Temperature of Rooms.— This accounts 
for the relaxing effect of external heat — the languor 
and lassitude of those who spend their days and nights 
in heated apartments. This effect is often heightened 



220 HYGIENE. 

by imperfect ventilation, suffering the air to become 
loaded with carbonic acid and other impurities, The 
stomach seldom digests food when there is no demand 
for it in the system ; and if food be taken under these 
circumstances, indigestion must follow. 

Living-rooms, school-rooms, offices, etc., should be 
maintained as nearly as possible at a temperature be- 
tween sixty and sixty-five degrees. This will leave 
some thirty-five degrees of temperature to be supplied 
by the vital apparatus, and that will insure, as a con- 
sequent, sufficient force to give energy and efficiency 
to the life-functions. Sleeping apartments may safely 
have a lower temperature — say fifty degrees. 

321. Means of reducing Heat. — In the artificial heat 
produced by the burning of fuel, we have a means of 
guarding against low temperature, that may be made 
available in all in-door occupations; and proper cloth- 
ing, exercise, breathing, and food will render out-door 
employments comparatively comfortable in any ordi- 
nary temperature. But the other extreme, the high 
temperature of summer, is not so readily controlled; 
much may be done, however, in this direction that 
has hardly been attempted yet. 

Buildings with thick walls, or with an air-chamber 
between the outer and inner surface, will maintain a 
much more uniform temperature than can be secured 
by the walls in common use. The evaporation of water 
is the method employed in nature to mitigate extreme 
heat every-where. The three great oceans which stretch 
across the tropics present a broad evaporating surface, 
which serves to cool the trade-winds that sweep over 
the continents. If the entire surface of the globe 



ANIMAL HEAT. 221 

within the tropics wore land, neither animal nor 
vegetable life could be sustained on it. 

333, Exposure to currents of Air. — Evaporation 
may be made available, to some extent at least, to cool 
down the intensity of summer heat in and around our 
dwellings. While our clothing should allow the air to 
penetrate freely, that the perspiration may evaporate 
easily from the surface of the body, yet care must be 
taken lest currents of dry air produce such rapid evap- 
oration as to arrest or obstruct the perspiration by a 
sudden reduction of the temperature. 

It is always safer to have the evaporation take place 
from the surface of our clothing rather than directly 
from the skin. The influence of even a rapid breeze, 
when we are perspiring freely, may be borne with 
little danger if w r e continue in active exercise; but 
when the exercise is suspended, currents of air should 
be avoided, and additional clothing should be put on. 

Recapitulation. 

Temperature of the healthy body is uniform. Evaporation is 
a regulator of temperature. Proper breathing, appropriate food, 
and a healthy condition of the skin are necessary to a uniform 
heat. Precautions should be taken against a cold atmosphere 
by those who have weak or diseased lungs. Overheated rooms 
are to be guarded against. Proper temperature of living-rooms 
is between sixty and sixty-five degrees Fahrenheit. Evapora- 
tion is the natural means of reducing temperature. When 
heated, avoid currents of air. 



222 HYGIENE. 



LESSON XL. 

BATHING — CLOTHING. 

323. Bathing necessary. — In order to maintain a 
uniform temperature of the body, the skin must be 
kept in a healthy condition, so that when the heat of 
the body rises above ninety-eight degrees, perspiration 
will be increased, and evaporation will reduce the 
temperature to the healthy standard; or, on the other 
hand, if the heat of the body falls below that standard, 
the action of the skin will be proportionally dimin- 
ished, and the animal heat thus preserved. But in 
order that the skin may thus act as a regulator of 
animal heat, it must be kept clean. It is one of the 
channels through which the waste material of the 
body is carried away. 

When the perspiration evaporates, it leaves on the 
surface of the skin the saline and animal matter which 
it held in solution. But the skin secretes oil, also; and 
this, with the residuum from the evaporation and the 
natural waste from the surface of the cuticle, forms a 
gummy substance which is liable to obstruct greatly 
the natural outlets through the skin. 

324. How to Bathe. — To remove this accumulation, 

as well as that which is added to it from external 
sources, the whole surface of the body should be fre- 
quently and carefully washed. Bathing, as a means of 
cleansing the skin, should be resorted to, during the 
warm seasons, at least as often as twice a week. The 
bath should be of soft water, and the temperature be- 
tween ninety and one hundred and ten degrees. In 



B ATH ING — CLOTHING. 223 

order to dissolve the oily accumulations more certainly, 
fine soap should be used moderately, and the surface 
briskly rubbed with a soft sponge, and dried with a 
coarse towel. 

Care must be observed in the use of strong potash 
soap, in bathing, lest the oil should be so completely 
removed from the cuticle that its surface will be ex- 
posed to the air, and become dry and chapped from its 
action. If soft, warm water be used, nothing but the 
mildest soaps will be necessary to cleanse the skin 
effectually. 

325. Bathing for other Purposes. — Bathing may be 
resorted to for other purposes than that of cleansing the 
skin. Where the cutaneous circulation is feeble, and 
the temperature of the surface habitually too low, a 
hot bath may be taken for the purpose of inviting the 
circulation to the surface. For this purpose the tem- 
perature of the bath may range between one hundred 
and twenty and one hundred and thirty degrees. Those 
who resort to the use of the hot bath must be careful 
not to suffer its use to grow into a habit. 

What we have already said (Lesson XXXIX) on the 
subject of overheated rooms, applies equally to any 
other habitual substitution of external heat for that 
which is produced by the chemical changes going on 
in the living body. If the vital force be not very 
feeble, the circulation may be attracted to the surface 
as certainly and more permanently by a cold bath — 
or, rather, by the reaction which follows a cold bath — 
than by the direct application of heat. To secure this 
object, the bath should have a temperature of about 
seventy degrees, and should not be continued more 



224 HYGIENE. 

than two or three minutes, being followed by brisk 
friction on the surface with a coarse towel or hair- 
cloth. 

320. The Plunge-bath and Shower-bath. — The 

bath may be used for the purpose of rousing up the 
sluggish action and torpid sensibilities of the body. 
To accomplish this end, the whole body should be 
plunged at once into water of a temperature between 
sixty and seventy degrees, and immediately wiped dry, 
and wrapped in a soft blanket or clothed in flannel. 
The same purpose can be accomplished as effectually 
and sometimes more conveniently by a shower-bath. 
But in the use of both the plunge and shower-bath 
we must be careful not to mistake an exhausted vitality 
for a merely torpid condition of the system. 
. In general it will be safer to begin either the plunge 
or shower-bath with a temperature of eighty degrees, 
and if the bath is followed by a glow of heat on the 
surface, we may safely venture to reduce the tempera- 
ture; but if not, we should at once desist. Medicated 
and vapor-baths are frequently used, but, being reme- 
dial agents, they do not belong to the subject of 
hygiene. 

327. Clothing, as related to health. — To enable 
the skin to perform its office in such a manner as to 
regulate effectually the temperature of the body, care- 
ful attention must be paid to the subject of clothing. 
This embraces both the material used in the fabrics 
worn, and the adjustment of it to the body. 

So far as the subject is related to health, the prime 
object of clothing is to protect the surface of the body 
from vicissitudes of temperature, by interposing between 



BATHING — CLOTHING. 225 

it and the external air a non-conducting substance, 
which will transmit the heat of the body but slowly 
when the air is colder than blood-heat, and which 
will arrest the scorching heat of the sun, when his rays 
have a temperature above the natural heat of the body. 
Substances differ widely in their conducting properties; 
but in the fabrics used for clothing, the chief difference 
consists in the porous texture of the cloth, or the 
amount of air in the fabric. 

328. Qualities of Good Clothing. — Wool, when 
carded and spun in the ordinary manner, forms an 
elastic, soft, and porous texture, and is therefore an 
excellent non-conductor of heat; but the same wool, 
if combed so that the fibers will lie parallel, will form 
a firm, hard, worsted thread, which, when woven, will 
be almost as good a conductor as linen. Cotton spun 
with a slack twist, and softly woven, wall conduct heat 
but little better than flannel ; but if hard twisted and 
firmly woven, cotton goods conduct heat freely. 

Another important property of a good material for 
clothing is, that it shall not absorb and retain moisture 
to any considerable extent. A good clothing material, 
while it will not permit a current of air to pass 
through it directly, yet it must be so porous as to 
transmit the insensible perspiration without obstruc- 
tion. 

329. Variations of Clothing. — Clothing should be 
varied with the climate and season, but this variation 
should have regard more to quantity than quality of 
clothing. In hot climates, and in warm weather in all 
climates, few r er garments should be worn, and those of 
lighter fabrics; but still a non-conductor is needed, to 



226 HYGIENE. 

prevent the injurious effects of sudden changes of tem- 
perature, from currents of air, or transitions from sun- 
shine to shade. The direct rays of the sun in the 
summer months frequently give a temperature far 
above blood-heat, and persons exposed to this require 
the protection of the best non-conductors they can 
command. 

The materials of clothing in common use are fur, 
wool, silk, cotton, and linen; and their value as cloth- 
ing material is in the order they occupy in this list. 
For protection against intense cold, fur is the best dress 
material known. Its high price and the difficulty with 
which it is cleansed are the principal objections to its 
general use as winter clothing. 

330. Wool, Silk, Cotton, and Linen. — Fine wool, 
made into loose, soft fabrics, is the best substitute for 
fur, and, indeed, meets all the demands of comfort, 
health, and beauty in dress material. Silk is a good 
non-conductor of heat, and absorbs very little moisture, 
but its high price has hitherto prevented its general 
use in dress. Cotton has a wide range in its conduct- 
ing properties, depending on the mode of its manu- 
facture. Cotton flannels are nearly equal to w T oolen 
fabrics as nonconductors, while the hard-twisted, 
closely-woven shirtings differ but little from linens 
in this respect. 

From the round, hard character of the fiber, flax and 
hemp, in all the forms of their manufacture, are good 
conductors of heat, and consequently the worst material 
for clothing in use. White linen, worn as an outer 
garment, is a good reflector of sunshine. This, to some 
extent, counteracts its defect as a conductor. Under- 



HYGIENE OF BONES. 227 

clothing should be changed frequently and kept scrupu- 
lously clean. 

Recapitulation. 

A healthy action of the skin is important in maintaining a 
uniform temperature. To secure this, frequent bathing is neces- 
sary. Bathing may be used as a means of influencing the 
circulation of the blood. Caution in the use of warm baths. 
Eules for using the plunge-bath and shower-bath. 

Clothing is directly related to health. A good clothing mate- 
rial must be an imperfect conductor of heat. Mode of manu- 
facture has much to do with the conducting property of cloth- 
ing materials. 



LESSON XLI. 



HYGIENE OF BONES. 



331. Bone Nutrition — its demands. — The apparatus 
of voluntary motion is much less complicated than that 
of either of the other systems, and consequently less 
liable to derangements and disturbances of its functions. 
The osseous or bony frame-work of the body, for its 
proper development and the maintenance of its healthy 
action, demands attention to food, exercise, and security 
from external injuries. 

The food necessary to supply the material for the 
formation and repair of bone, consists of those articles 
which are rich in phosphate of lime, such as fish and 
other forms of animal flesh, eggs, wheat bread, etc. 
Many vegetables and fruits, which are otherwise very 



228 HYGIENE. 

nutritious, are nearly destitute of bone-earth, and per- 
sons living on these exclusively can not develop and 
maintain a healthy bony system. Potatoes, for example, 
while they are rich in the starchy elements of food, and 
contain a fair proportion of the nitrogenous or muscle- 
forming material, are deficient in bone-earth; and the 
bones of persons living exclusively on such diet become 
soft and often distorted. 

332. Oversupply of Bone-earth — its effects. — Per- 
sons who are very fond of what they please to call good 
living — that is, a diet rich in animal food — frequently 
suffer from an oversupply of bone-earth. The bones 
become hard and brittle, and even slight accidents 
result in fractured bones, often seriously endangering 
life. This redundancy of phosphates in the food may 
give rise to gouty concretions about the joints, resulting 
in a disease alike troublesome, painful, and difficult to 
cure. 

These two conditions frequently mark the opposite 
extremes of society. Rickets and other bony deformi- 
ties indicate the poor diet of the children of want, 
while fractured bones from slight accidents, and gouty 
ailments, are the results of affluence and ease. The 
remedy for both lies in a rational diet and proper 
exercise. 

333. Distortion of Bones— how produced. — Both 

the size and strength of the bones composing the frame 
of the body will depend much on the judicious use of 
them. Like every other organ of the body, the bones * 
during the period of growth require regular exercise, 
in order to their full development both in regard to 
their perfect organization and their proper size. But at 



HYGIENE OF BONES. 229 

this period all occupations which require a constrained 
or unnatural attitude of the body, or which demand 
hours to be spent in the standing position, should be 
carefully avoided. 

The bones of growing persons are quite soft and 
flexible, and will yield to a constant pressure; and 
if that force be applied in an unnatural direction, the 
bones will be permanently curved, and the body mis- 
shapen and deformed. Scholars at their desks should 
be required to sit upright, so that the w r eight may be 
supported vertically on the spinal column. 

334. Freedom of Motion necessary. — Persons fol- 
lowing sedentary employments should so arrange their 
work that they will not be required to assume a stoop- 
ing attitude. With all persons, such positions of the 
body are injurious to health, but, to the young, perma- 
nent deformity is almost certain to be added to the 
present injury. This mischief results not so much 
from assuming improper attitudes as from the con- 
tinuance of them. Children at natural, healthful play 
throw the body and limbs into almost every conceiv- 
able position, but they change their attitudes every 
moment, and no harm results. 

In childhood, the symmetrical development of the 
bony skeleton requires perfect freedom of motion, and 
such active employments or plays as will give a great 
variety of motions to the body, and a constant change 
of position. The perfect play of all the organs in 
mature life demands, as a first condition, that there 
be no malformation of the bones by careless or improper 
treatment in youth. 

335. Compression from Clothing. — The clothing 



230 HYGIENE. 

of young persons should be adjusted with special refer- 
ence to the fact that, while the bones are yet flexible 
from the large proportion of animal matter they con- 
tain, even a very gentle pressure, continued from day 
to day, will curve and distort the bones, and thus 
produce permanent malformation. 

In this manner the Chinese practically render their 
women cripples for life; and a tribe of savages in the 
Rocky Mountains, by a similar process, deform the 
head in childhood so as to produce a nation of mon- 
strosities; and thousands of children in this country, 
by a very moderate pressure on the floating ribs, 
continued through the growing period, have the chest 
so narrowed at the base as practically to diminish 
the breathing power at least one-half, and, as a con- 
sequence, reduce the force of all the vital functions in 
the same ratio. 

336. Deformed Feet — how produced. — Multitudes 
thus deformed in infancy drag out a miserable life, 
under the false impression that their daily suffering 
from feeble health is a mysterious visitation of Divine 
Providence. In childhood and youth, the dress of either 
sex should be so loose as to admit of the fullest inflation 
of the lungs without obstruction or constraint. 

In dressing the feet there is great liability to distort 
the bones of the toes and the metatarsal bones. But 
few feet can be found in this country which retain the 
natural form of the human foot, as seen in the statuary 
of the Greeks. Though this is a minor evil compared 
with the deformity of the chest, yet activity and grace- 
fulness of movement is greatly impaired by every de- 
parture from the natural form of the foot, and the 



HYGIENE OF BONES. 231 

ability to participate in that most healthful of all 
forms of exercise, walking, is proportionally reduced. 

337. Spinal Curvature — its origin. — Next to the 

ribs, the spinal column is most liable to permanent 
deformity from compression. We have already spoken 
of the stooping attitude, acquired at study or in follow- 
ing sedentary employments, but a greater danger is to 
be apprehended from a lateral or sidewise curvature, 
induced by working at occupations which employ but 
one hand and arm. 

The constant action of the muscles on one side, while 
those of the other remain inactive, will naturally tend 
to draw the dorsal portion of the spine toward that side. 
This tendency is often aided by an elevated position 
of the elbow of the active arm, or, in many instances, 
merely by a habit of drawing the shoulder of that side 
upward. This deformity is very common, to a greater 
or less extent, among needle-women, and is frequently 
seen among clerks who write at high desks. The de- 
formity is often so slight as to escape the notice of 
those suffering from it, or their friends, and yet it 
always impairs the powers of endurance. 

338. Exercise — its effects. — In adult age the bones 
become firm and solid, and are much less liable to be 
distorted or deformed by pressure than in early life; 
they are. however, subject to the general law of w r aste 
and repair common to all parts of the living machinery. 
This transformation takes place more slowly in bone 
than in the soft parts, but the health of the bone re- 
quires that it be carried on steadily and at a uniform 
rate. This demands active exercise in a good atmos- 
phere. 

B. P.— 20. 



232 HYGIENE. 

It has been demonstrated that the bones actually 
diminish in size, when persons accustomed to active 
labor suddenly change their habits of life and abandon 
their activities. But exercise may be carried to ex- 
haustion, and both bone and muscle may be diminished 
in size and impaired in strength by overwork. 

Recapitulation. 

Bone nutrition demands food sufficiently rich in phosphate 
of lime. Oversupply renders them brittle. Deformity of the 
skeleton may result from unnatural positions long continued. 
Freedom of motion and frequent change of attitude are neces- 
sary to secure a well-developed frame. Deformities are more 
easily produced in childhood than in mature age. Spinal curva- 
ture — how induced, and its effect on the general health. 



LESSON XLII. 

MUSCULAR EXERCISE. 

339. Muscular Motion. — The system of muscles, 
with their tendons and attachments, constitute the 
machinery of motion, which is operated by the vital 
force through the motor nerves. A general law, gov- 
erning all the vital machinery, provides that, within 
certain limits, an organ shall correspond with the work 
it is required to do. Under this law, the muscles 
increase, both in size and force, by their judicious use, 
and the supply of vital energy is correspondingly 
augmented. 

When the muscles are brought into use, there is 



MUSCULAR EXERCISE. 233 

an increased flow of blood to them, which demands a 
corresponding increase in the action of the whole cir- 
culatory apparatus; but this augmented circulation 
throws more blood to the lungs to be purified and 
aerated, and this requires fuller and deeper breathing. 
A larger flow of oxidized blood being transmitted 
through the capillaries, the chemical changes, both in 
the tissues themselves and in the combustible elements 
of the food, are directly increased. 

310. Influence of Exercise. — Now this complicated 
chain of causes and effects, springing from muscular 
contraction, terminates in two important results : first, 
the cell structure of the muscles themselves is more 
frequently renewed, by which means the contraction 
of the muscle is rendered more efficient; and if the 
demand is kept up by habitual activity, the number 
of cells will be increased, thus giving greater volume 
and density to the muscles that are in frequent use. 

In the second place, the chemical change connected 
with the renewing of the tissues — the removal of the 
old matter and depositing of the new, as well as the 
rapid oxidation of the carbon and hydrogen of the 
food — is directly connected with the evolution of vital 
force. This not only serves to increase the power of 
muscular contraction, but it re-inforces all the vital 
functions and imparts activity to the mind. 

311. Muscular Activity and Good Health. — This 

activity of the muscular apparatus, terminating in an 
increased waste of material, with a correspondingly 
augmented force distributed to all the organs, calls for 
a supply of new material to be furnished by the di- 
gestive apparatus. This is the only legitimate and 



234 HYGIENE. 

natural means of creating an appetite ; for it not only- 
demands the food, but at the same time supplies the 
force for its speedy and perfect digestion. But while 
it furnishes vital force for the digestion of the addi- 
tional food demanded, this is only the measure of the 
augmented vital force of all the organs. Muscular ac- 
tivity is, therefore, to be regarded as the first link in 
the chain of phenomena leading to, and securing that 
very desirable result, good health. More or less directly 
connected with a vigorous exercise of the muscles, 
stands the healthy performance, correct habit, and 
persistent endurance of all the functions of life. 

342. Exercise as a corrective. — If a person has 
contracted a vicious habit of imperfect and shallow 
breathing, vigorous exercise will soon compel a free 
and full use of the lungs, and directly establish a more 
correct habit of breathing. If sedentary employments 
endanger a curvature of the spine, a brisk walk of 
half an hour, once or twice a day, will be found the 
most effectual remedy. The almost instant fatigue of 
walking in a bent posture will compel the erect atti- 
tude as a means of relief. 

But muscular exercise has its healthful restrictions. 
It should never be violent, nor should it be continued 
to fatigue. Whatever form of exercise may be selected, 
the action should commence moderately and be gradu- 
ally increased to the proper intensity. Active forms of 
exercise should not be suddenly suspended; and if the 
exercise has produced perspiration, additional clothing 
should be put on. 

343. Pure Air for Exercise. — Exercise should be 
conducted in the open air, if we would derive from it 



MUSCULAR EXERCISE. 235 

the greatest benefit. If the air we breathe be vitiated 
by a mixture of unwholesome gases, or if its proper 
proportion of oxygen be reduced by having been pre- 
viously breathed, the good effect of exercise on the 
vital force is lost, and even a positive injury may be 
the result. 

Muscular activity can be continued longer in the 
open air, without producing a sense of fatigue, than 
in a close room. An invalid w T ill sit up longer when 
riding in a carriage, than in an easy chair in the sick- 
room. If, however, the condition of the weather forbids 
mit-door exercise, or circumstances render it inconven- 
ient, the windows may be thrown open and the room 
freely ventilated, so that a good substitute for the free 
air of out-doors may be had, which will be much better 
than omitting the exercise. 

3J4. Sunlight. — Light exerts a curious influence on 
the ability to endure exercise without suffering fatigue. 
Repeated experiments have demonstrated that persons 
can endure labor with less fatigue in the sunshine 
than in the shade, the temperature being the same. 
We shall, perhaps, never know how the sun's rays 
impart force to both vegetable and animal life, but 
the fact may be ascertained every day. 

Kitchens and workshops should be well lighted, as 
well as ventilated, and living-rooms should be on the 
sunny side of the house, and the light should be freely 
admitted. Miners, and others who work by artificial 
light, are, as a general rule, short-lived, and have a 
feebler vitality than those who enjoy sunshine. In- 
valids, and persons confined by chronic forms of disease, 
should have light, cheerful rooms. 



236 HYGIENE. 

345. Amount of Exercise. — Exercise, whether in 
the form of manual labor, or taken expressly for its 
sanitary effect, should be reduced to a habit, and 
should have its regular periods of activity and rest. 
The amount of exercise necessary to secure its best 
effect is modified by so many circumstances, that no 
special rule can be given. The general law governing 
exercise, as we have elsewhere said, is that it is bene- 
ficial up to the point of fatigue; but as soon as this 
feeling is distinctly perceived, exercise should be sus- 
pended at once. 

Persons who are beginning a course of active exercise 
will soon reach this point, but each succeeding day 
they will find themselves able to continue the exercise 
longer, and even add to its force and activity, until 
eight or ten hours of the day may be devoted to 
active labor, without materially impairing the vital 
energy. Fatigue is more readily induced by the vio- 
lence of the exercise than by its long continuance. A 
person who will walk a mile in thirty minutes and 
feel no fatigue, will be entirely exhausted after run- 
ning that distance in ten minutes. 

346. Mental Functions and Exercise. — The mental 

condition during exercise is of the first importance in 
regard to its sanitary value. If exercise be imposed as 
a daily task — if it be taken as a medicine to secure 
health, it will soon become irksome, and even repul- 
sive, and no good will be derived from it. Whatever 
may be the form of exercise, the mental action should 
be directed to some other point than that of the mere 
muscular motion. 

If walking is selected, the mind should be pleasantly 



EXERCISE AND REST. 237 

employed on some subject entirely disconnected from 
the exercise itself. The muscular movements of walk- 
ing should be performed entirely by the reflex action 
of the spinal cord. 

Recapitulation. 

Judicious exercise increases both the volume and force of 
muscles. It hastens the renewal of the tissues, and thus con- 
duces to good health. Exercise should be in the open air 
when possible, for in a vitiated air it soon produces fatigue. 
Sunlight has an invigorating influence on all the vital func- 
tions. Exercise should be habitual, and the attention should 
be directed to some other object. 



LESSON XLIII. 



EXERCISE AND REST. 



347. Rules of Exercise. — Summing up what has 
been said on the subject of exercise, we present the 
following rules, namely: 

1st. It should call into play the largest number of 
muscles, and include such a variety of attitudes and 
motions as to distribute the exercise over the whole 
body. 

2d. The movements should be energetic and active, 
but never violent. 

3d. The exercise should carry with it some mental 
stimulant, or it should leave the mind free to employ 
itself on other subjects without interfering with the 
muscular movements. 



238 HYGIENE. 

4th. It should be regular and habitual. 

5th. It should have the full advantage of free air 
and light. 

6th. It should begin gradually, and be increased to 
full energy. 

7th. All kinds of exercise should be avoided which 
require the muscles to be held long in a state of rigid 
contraction. 

348. Gymnastics. — In selecting a form of exercise to 
fill these indications, we have a wide field in which to 
make our choice ; and yet but few of the special modes 
which have been invented and prescribed as sanitary 
measures, are free from formidable if not fatal objec- 
tions. The various forms of gymnastics and calis- 
thenics, while they fill most of the requirements, 
fail to furnish any mental stimulus other than the 
muscular movements themselves; and yet these de- 
mand so much of the attention, that the mind can 
not leave the movements to seek other fields of em- 
ployment. 

The various games of ball, etc., while they call 
into activity a wide range of muscles, and have the 
advantages of open air and ample light, and, withal, 
furnish a vigorous mental stimulant in the chances 
of the game, yet there is a constant tendency for 
that activity to be converted into violence, that may 
end in actual injury, and more than defeat the object 
of the exercise. 

349. Manual Labor. — Walking, when properly per- 
formed, is one of the most healthful forms of exercise, 
and one which is nearly always available. We said, 
when properly performed, for every body has not learned 



EXERCISE AND REST. 239 

to walk correctly. A promenade should always be per- 
formed in the open air, with the body and head erect, 
and the shoulders thrown back so as to give free ex- 
pansion to the lungs. The clothing should be adapted 
to the condition of the weather, and should be so ad- 
justed as to permit the free use of every muscle of the 
body, without compression or restraint. 

But the demand for active exercise finds its legiti- 
mate and complete fulfillment in the various, forms of 
useful labor. This is demonstrated every day in the 
fact that the most perfect symmetry of form and vigor 
of constitution is found among those w T ho spend most 
of their waking hours in manual labor. Labor only 
requires to be regulated by a proper knowledge and 
correct application of physiological laws, to meet all 
the demands of healthful exercise. 

350. Kinds of Labor not Healthy.— But all forms 
of labor are not alike promotive of health. That form 
of it is best which furnishes the greatest variety and 
widest range of activities. These conditions are found 
in the highest perfection in agricultural and horticul- 
tural pursuits. The division of labor w T hich, in our 
modern civilization, has been carried to so great an 
extent, and which has resulted in such a wonde?ful 
economy of labor, has a direct tendency to reduce its 
value as a means of maintaining good health. 

The tendency of this system is to confine the work 
to the repetition of a few motions — the activity of a 
part, and often but a small part of the body; and while 
these organs are generally overworked, the remainder 
of the body becomes feeble from disuse. Some occu- 
pations employ the hands alone, while the other 
B. P.— 21. 



240 HYGIENE. 

muscles of the body are unused and the brain unem- 
ployed. Such occupations are pernicious to health, 
and should be avoided. 

351. Bad effects of Overexercise.— But exercise, 
like every other good thing, is liable to be abused, and 
thus become a positive injury and a fruitful source of 
disease. It is only when labor is perverted that it de- 
generates into drudgery and becomes a curse, destroy- 
ing the symmetry of the body, entailing on its victim 
disease and suffering, and greatly reducing the period 
of human life. 

The tendency of modern society is to inflict positive 
injury on a large class, by idleness and want of any 
healthful exercise, and to break down the constitution 
and ruin the health of another class by overwork. 
Eight hours of labor — active, but not violent — with an 
interval of one or two hours' rest, will, in most consti- 
tutions, be endured, without loss of energy or injury to 
health, for six days in succession, and, with a day of 
rest intervening, may be repeated from week to week 
indefinitely. A few may endure more than this, but 
these are the exceptions and not the rule. 

352. Exercise for Young Persons.— Young persons 
in active employments need more frequent intervals 
of rest than those of mature age; and the same is 
true in regard to exercise, if confinement is the rule. 
Pupils required to remain quiet in the school-room, 
should have at least fifteen minutes of active exercise 
at the end of each hour. Such a course would not only 
secure better health to the scholars, but a more satisfac- 
tory progress in their studies. 

Persons laboring in shops will greatly improve their 



EXERCISE AND KEST. 241 

health by devoting an hour each day to amusement 
in the open air and sunlight. This is especially true 
of those occupations which employ only the hands, or, 
possibly, only a single hand. Such persons require 
as much exercise of the whole body as their health 
would demand if they were actually unemployed. 
Boys generally manage to get exercise enough ; and 
if girls from fourteen to twenty years of age w r ere 
compelled to exercise every day in the open air, we 
should soon have a different race of women. 

353. Rest — its necessity. — But vital machinery is 
not made for constant activity. A regular alternation 
of action and rest is the law of life every- where, and 
the intervals of repose are as essential to health as are 
the periods of activity. Rest is rendered necessary 
from two considerations: In the first place, the cells 
composing the muscular fibers are broken down and 
removed more rapidly during the active contraction of 
the muscle, than the nutritive process is able to re- 
place them; but while we rest, the preponderance is on 
the other side — the wastes are replenished and the 
muscular tissue restored to its original integrity. 

In the second place, active exercise expends force 
more rapidly than it can be supplied by the brain and 
nerves: hence, as fatigue comes on, the muscles con- 
tract more slowly and with less energy, until finally 
the entire exhaustion of strength, above what is neces- 
sary to keep in motion the involuntary organs, takes 
place, and motion ceases from prostration of the vol- 
untary powers. 

354. Two kinds of Rest. — Corresponding to this 
division, rest must be of two kinds, looking to the 



242 HYGIENE. 

accomplishment of these two objects. A mere suspen- 
sion of muscular contraction is all that is necessary to 
restore the wasted tissues, for nutrition will go on 
with an activity stimulated by the demand for new 
matter, while the waste from action will be suspended. 
Under these influences, but a short period of repose 
will be required to restore the equilibrium. 

That rest is most perfect, however, which most 
completely suspends muscular action; and from this 
it follows, that a reclining position is better adapted 
to rest than either sitting or standing. But to restore 
exhausted contractile force, requires more than mus- 
cular repose : it demands brain rest, which can only 
be had in sleep. 

Recapitulation. 

General rules for exercise. Gymnastics do not furnish any 
mental stimulus other than the muscular movements them- 
selves. Walking is a healthy and available form of exercise. 
Manual labor properly regulated is most conducive to health. 
Kinds of labor which are to be avoided. Kest must follow 
activity. Muscular rest, distinguished from brain rest. 



LESSON XLIV. 

BRAIN REST. 

355. The Nervous System. — The systems of nutri- 
tion and voluntary motion, which we have been con- 
sidering, are entirely dependent on the nervous system 
for the supply of force necessary for their several 
functions. All the diseases of these systems which 



BRAIN REST. 243 

do not depend on structural derangements of the 
organs, are therefore to be traced to disturbances in 
the nervous system. 

But this dependence is reciprocal. The brain de- 
pends on the digestive apparatus for a constant supply 
of healthy blood, rich in the elements of brain nutri- 
tion. It is also dependent on the uninterrupted action 
of the respiratory organs, for a supply of oxygen neces- 
sary to carry forward the chemical changes so inti- 
mately connected with the evolution of that vital force. 
Without the chemical changes dependent on digestion 
and respiration, the supply of vital force is cut off; 
and without a healthy action of the brain and nerves, 
its distribution is impossible. 

356. Brain needs Exercise. — The brain and its 
appendages are subject to the general physiological 
law of alternate activity and rest, which is so inti- 
mately connected w r ith the normal condition and 
healthy action of all the other organs of the body. 
As the brain is the most delicately organized part of 
the body, and receives proportionally the largest supply 
of blood, its tissues are transformed with a correspond- 
ing rapidity. 

If the exercise of brain be regular, and not too 
violent nor too long protracted, and the nutrition be 
sufficient to supply the material wasted by the activity, 
the result of the exercise will be the same here as else- 
where. The efficiency of brain action will be in pro- 
portion to the frequent and perfect renewal of its cell 
structure. The functions of sensation and motion do 
not exhaust the cerebrum as rapidly as the function 
of thought. 



244 HYGIENE. 

357. Brain fatigue. — During our waking hours, 
there is hardly such a thing possible as absolute brain 
rest. The attention is constantly called to the various 
objects of sense around us, and the perceptive faculty is 
as constantly required to note the various sensations, 
so that the representative faculty can recall them at 
pleasure. 

It is true that, under ordinary circumstances, this 
action is so nearly spontaneous that it can hardly be 
called brain labor. But let a person spend a day in 
sight-seeing, in some new and interesting locality, or 
listen closely for an hour or two to an intricate argu- 
ment, or an elaborate discourse on any subject that 
secures his attention, and a sense of brain weariness 
will be felt. The undivided attention can no longer be 
fixed and held to the subjects of observation, and the 
mind will fail to grasp the scope of the argument, or 
perceive the nice distinctions which the speaker, from 
familiarity with his subject, may present even with 
great clearness. 

358. Brain weariness. — This point of mental fatigue, 
or brain weariness, is induced more readily in young 
persons than in those of mature age, and in that class 
who are not accustomed to brain work, than in those 
whose business has been study. This fact is especially 
commended to the notice of parents and teachers. 

Pupils, at the immature age of ten or twelve years, 
are required to confine their attention, often for a 
period of eight hours a day, to studies which are 
frequently abstruse, uninteresting, and, to them, diffi- 
cult; and this, generally, with but very brief intervals 
of rest. After an hour or less of close application to 



BRAIN REST. 245 

study, if the pupil be required to divert the brain 
action in the direction of brisk muscular exercise, 
involving chiefly the functions of the spinal cord, the 
brain will return to its task refreshed, and in this 
manner it may labor safely and profitably five or six 
hours a day. 

359. Mental effort long continued. — ^Lfter a period 
of close mental application, if the pupil finds himself 
unable to confine his attention to the subject of his 
investigation, or discovers an inability to exercise his 
ordinary powers of mental perception, he should be 
admonished at once and intermit his labors. All exer- 
tion beyond this point is more than a waste of time 
and effort; it is inflicting a positive and, to some 
extent, a permanent injury on the brain. If exertion 
be persisted in after this stage, a condition of ex- 
haustion will follow, from which recovery can be found 
only in sleep. But sound, refreshing sleep is not always 
attainable under these circumstances. 

The system of cramming, which is becoming so 
common in our schools, and which prescribes for pupils 
of tender age an amount of mental labor that would 
be more than enough for well matured and disciplined 
minds, has a tendency to arrest mental development 
by overwork. 

360. Time of Study. — No general rule can be laid 
down prescribing a definite number of hours of mental 
labor to each pupil in a school. So many modifying 
circumstances may interpose, such as age, sex, general 
health, temperament, previous habits of study, etc., 
that the whole matter must be left to parents or 
teachers, to be governed by their judgments under 



246 HYGIENE. 

very broad instructions. Before the age of ten years, 
study should be amusement rather than business; be- 
tween ten and fifteen years, the confinement should 
not exceed an hour of close application without inter- 
mission. 

As a general rule, boys endure confinement to study 
better than girls, and persons of bilious better than 
those of a nlrvous temperament; but those who are 
least able to sustain a protracted effort, can generally ac- 
complish more, by close application, in a given time, than 
those who suffer less from long continued mental labor. 



*.o 



361. Special Training. — In cultivating and devel- 
oping the mental powers, the same law governs the 
process as that which controls the education and train- 
ing of muscular movements. If the entire attention be 
directed to the training necessary to the performance 
of a single motion or group of motions, great perfection 
may be attained in that direction; but all the other 
movements being neglected, the aggregate of muscular 
power is reduced, and the educated faculties soon fail 
for want of the force which can be evolved only in the 
symmetrical development of all the faculties. 

Conforming to this law, it follows that, if the mental 
faculties be educated in a single direction, a much 
higher perfection is attainable, in that particular line, 
than would be possible if the culture and training 
were distributed equally among all the faculties. But 
the few favored faculties, depending on the general 
brain force for the power of their expression, and this 
failing through neglect of general culture, soon reduce 
the overtrained powers to the imbecility of the neglected 
faculties. 



BRAIN REST. 247 

962. Relation of Mind to Matter. — Many well- 
disposed persons object to referring the mental mani- 
festations, in any case, to the proper development and 
healthy action of the brain, because of a supposed tend- 
ency to materialism. But the relation of mind to 
matter is a question of fact, and is independent of all 
theory. 

Nothing is clearer than that all our knowledge of an 
outer world, as well as our knowledge of the thoughts 
and actions of other minds, reach us through sensation ; 
and, on the other hand, that we can transfer our 
thoughts to other minds only by muscular motion. 
But sensation and motion are primary brain functions. 
There is no necessity, however, for confounding the 
agent which operates, with the instrument by means 
of which the operation is performed. 

Recapitulation. 

There is a mutual dependence between the brain and the 
other organs of the body. All vital action is dependent on a 
healthy condition of the brain. The brain requires exercise in 
order to maintain its powers of action. Of the three brain 
functions, thought is the most exhausting. Brain labor de- 
mands frequent intervals of rest. Protracted study most in- 
jurious to young persons. Special training operates unfavorably 
on the general development of mind. 



248 HYGIENE. 



LESSON XLV. 

BRAIN POISONS. 

363. Alcohol, Tobacco, and Opium. — It may be 

regarded as an axiom in hygiene, that the proper devel- 
opment and healthy action of the brain and nerves, in the 
absence of structural derangements in the other organs, is 
the prime condition of good health. This being true, it 
follows that our first care in the preservation of health 
is to guard well the brain, supply it with pure, well 
aerated blood, give it the proper alternations of exer- 
cise and rest in each of its threefold functions, and 
preserve it from the influence of poisons which impair 
its powers, disturb its functions, or derange its delicate 
structure. 

Of this class of poisons the most dangerous are alco- 
hol, opium, and tobacco. Two of these, at least, are in 
common use in this country, and the third (opium) is 
rapidly gaining favor with certain classes in American 
society. If we had the means of tracing to its legiti- 
mate source every disease that afflicts civilized man, 
we have no doubt but that a large majority would be 
found to originate, either directly or indirectly, in the 
habitual use of these narcotics. 

364. Alcohol — its chemical relation. — Alcohol is 
the most active, and on this account, as well as on 
others that will appear hereafter, it is the most 
dangerous of this class of poisons. Alcohol is the 
product of fermentation; the result of, or, rather, one 
of the bodies resulting from, the decomposition of 
sugar. If it is produced from grain, potatoes, etc., 



BKAIN POISONS. 249 

the starch is first converted into sugar, and this into 
alcohol and carbonic acid: the one a poison when taken 
into the stomach, the other a most deadly poison when 
inhaled. 

In all the various forms of intoxicating liquors, the 
active agent is alcohol; and the effect of a given quan- 
tity of it is the same, whether in the concentrated form 
of distilled liquors, such as brandy, rum, gin, or whisky, 
or in the milder dilutions of fermented mixtures, such 
as wine, beer, cider, etc. In all these mixtures the 
fluids with which it is mixed serve only as solvents 
of the alcohol, and do not decompose it nor change its 
character. 

365. Alcohol and Organic Substances, — Though 
alcohol produces its chief and most observable effect 
directly on the great nervous centers, yet there is an 
indirect action through the nutritive functions, which 
is too important to be overlooked. The chemical action 
of alcohol is to arrest or impede change in organic sub- 
stances wherever it comes in contact with them. 

Animal tissues may be preserved in alcohol for an 
indefinite period, so as to be entirely proof against 
the putrefactive process. Vegetable substances, also, 
may be preserved from decay indefinitely by immer- 
sion in alcohol. But the life processes, from the first 
stage of digestion to the completed w r ork of trans- 
forming the tissues, is incessant change; and whatever 
interferes with this regular succession of chemical trans- 
formations, in the same proportion disturbs the vital 
functions and impairs health. 

366. Alcohol is Indigestible. — The first effect of 
alcohol, when taken into the stomach, is to impair 



250 HYGIENE. 

the capability of change in the food in the process 
of digestion, for digestion consists of a series of chem- 
ical changes. Beefsteak that has been macerated in 
alcohol for forty-eight hours is perfectly indigestible. 
Although the brandy taken at dinner impairs di- 
gestion while it is present in the stomach, yet a 
wise provision is made by which the stomach is soon 
relieved of its presence. 

Alcohol is entirely indigestible, and does not pass 
with the chyme into the intestinal tube, but is in- 
stantly taken up by the absorbents and carried into 
the veins, and by way of the right side of the heart 
and pulmonary artery, it reaches the lungs and begins 
to escape with the breath exhaled. That which gives 
odor to the breath of one who drinks is, substantially, 
pure alcohol. A very small part of it has lost one- 
third of its hydrogen, and is converted into a compound 
which chemists have named aldehyde. 

367. Alcohol impairs Chemical Change. — Though 
the odor of alcohol can be detected in the breath a 
few minutes after it has been taken into the stomach, 
yet it is not all disposed of so soon, for the odor fre- 
quently remains on the breath for twenty-four hours. 
All this time the poison has been mixed with the 
blood, and passing the capillary circulation, it has 
produced its specific effect on the changes, so inti- 
mately connected w T ith life itself, going on in this 
region of waste and repair. These changes consist in 
the oxidation of the carbon and hydrogen of the di- 
gested food, and the consequent evolution of animal heat 
and vital force. 

That it really impairs all these actions and dim- 



BRAIN POISONS. 261 

inishes change in the capillaries, and consequently 
reduces the normal amount of vital force by which the 
nervous system is enabled to maintain the various 
voluntary and involuntary motions necessary to life, 
is no longer a matter of conjecture. It has been dem- 
onstrated that, under the influence of alcohol, the 
amount of carbonic acid exhaled from the lungs is 
diminished from thirty to fifty per cent. 

368. Alcohol lessens Muscular Force. — This reduc- 
tion of the chemical changes going on in the capillary 
circulation indicates a corresponding change in the 
brain force, as transmitted by way of the motor nerves 
to the muscles by which the various movements of the 
body are performed. This deduction of science has 
been fully demonstrated by repeated experiments, made 
by actual measurement of muscular power in the same 
individual under the influence of alcohol and without 
it. These experiments prove that the reduction of 
strength is very accurately measured by the diminution 
of carbonic acid from the lungs in breathing. This 
reduced supply of nervous force is soon apparent in 
the impaired powers of endurance, observed in those 
who use alcoholic drinks. 

369. Alcohol causes a sense of heat. — The effect 
of alcohol on the animal heat is among the most 
curious of the physiological phenomena that attend 
its action on the living body. The diminished pro- 
duction of carbonic acid, when under the influence 
of alcohol, would suggest a reduced combustion in the 
body, and a corresponding reduction of temperature; 
but the testimony of the person under its influence is 
conclusive in the opposite direction; he avers that he 



252 HYGIENE. 

feels warmer, and the flush of the blood in the super- 
ficial vessels appears to corroborate his testimony, 

Liebig, the justly celebrated German chemist and 
physiologist, attempted to solve the mystery by sup- 
posing that the oxygen inhaled entered into combina- 
tion with the alcohol, and thus produced heat without 
evolving vital force; but this solution will require an 
increased amount of carbonic acid in the breath, when, 
in fact, the quantity is diminished. 

370, The Thermometer shows a reduction of Tem- 
perature. — But the mystery disappears at once when 
we appeal to the thermometer. A delicate thermometer 
placed under the tongue will show an unsteadiness in 
the temperature for the first fifteen or twenty minutes 
after taking four ounces of brandy. In some instances 
the temperature falls from the first, but in most 
cases there is an increase of heat, ranging from one- 
half to three-fourths of a degree, and continuing from 
ten to fifteen minutes; after which there is a reduction 
in temperature of two or three degrees, lasting for sev- 
eral hours, even while the face is flushed and the person 
affirms that he is warmer. 

But common observation shows that he will freeze 
much quicker with than without the brandy. The 
flush of his face is the result of diminished action, 
suffering the blood to accumulate in the capillaries; 
and his sense of heat depends on perverted sensi- 
bility. 

Recapitulation. 

Narcotics operate as brain poisons. To this class belong alco- 
hol, tobacco, opium, etc. Of these, alcohol is the most active. It 
is the active principle of all spirituous and fermented liquors. 



BRAIN POISONS. 253 

When a given amount is taken, its effect is the same, whether 
concentrated or diluted. 

The chemical action of alcohol on organic substances arrests 
change. This impairs digestion, and diminishes vital force. 
The sense of heat following the use of alcohol is the result of de- 
ranged sensibility. 



LESSON XLVI. 



BRAIN POISONS — CONTINUED. 



371. Narcotic Poisons. — The direct action of alcohol, 
and other narcotic poisons, on the nervous system con- 
sists chiefly in diminished sensibility and its conse- 
quences. If the mouth be filled with a strong alcoholic 
liquor, such as brandy or whisky, and the same re- 
tained but a few minutes, it will be found that the 
sense of taste is nearly, if not entirely, destroyed for 
the time being. 

The mucous membrane of the stomach is continuous 
with that of the mouth: it will, therefore, be similarly 
affected by like agents. Alcohol will -produce a double 
effect on digestion : it will render the food less sub- 
ject to change, and, therefore, more difficult of diges- 
tion; and it will so reduce sensibility in the nerves 
of the stomach that the imperfectly digested food will 
be suffered to pass the pyloric orifice into the intestinal 
canal, and a great portion of the food be lost, if 
nothing worse occur from the presence of undigested 
food in the intestines. 

372, Alcohol and the Digestive Function. — But 



254 HYGIENE. 

this abuse of the stomach can not be long indulged in 
without permanently impairing the sensibility of that 
organ, and establishing the habit of imperfect diges- 
tion, if not inducing confirmed dyspepsia. The first 
effect of this impaired digestion is a demand for more 
food than would be required if digestion was perfect; 
for it is not the amount of food we eat that repairs the 
daily wastes of the body, but that which is digested 
and assimilated. 

This increased demand for food after taking the 
" bitters" is often mistaken for a healthy appetite, and 
regarded as an indication of increasing tone and vigor 
in the digestive apparatus. If the alcohol be left off, 
the returning sensibility of- the stomach will admonish 
the brain of the true condition of that organ, and its 
inability to digest food, and consequently it will refuse 
it, a loss of appetite being the result. 

373. Alcohol impairs sensibility. — The diminished 
sensibility in the nerves of the stomach is not a local 
affection, but extends to the whole sentient apparatus. 
It is to this fact that alcohol owes most of its reputa- 
tion as a medicine. It renders the patient insensible 
to pain, and he mistakes this insensibility for the cure 
of the disease, of which the pain was but the warning 
of a faithful sentinel. The insensibility to injury, of 
those who are intoxicated is very commonly noticed, and 
illustrates the effect of* this poison on the very impor- 
tant function of sensation. 

The general sense of feeling can not be impaired 
without the local senses suffering more or less. . Of 
these the sense of vision early feels the effect of the 
poison, rather in a perversion of vision than in a loss 



BRAIN POISONS. 255 

of sight. To intoxicated persons, things often appear 
double, and frequently things at rest appear to be in 
motion. The sense of hearing is less affected by alcohol 
than the other senses, and yet the long continued use 
of the poison often seriously impairs that faculty. 

374. Exhilaration. — The feeling of exhilaration, 
which is generally mistaken for exalted sensibility, is, 
in fact, the result of a partial paralysis of the sentient 
extremities of the nerves. The vital force, by the 
movement of which sensation is carried on, being with- 
drawn from the nervous expansions, is concentrated on 
the great nervous centers, thus manifesting the dis- 
turbed equilibrium of nervous force rather than an 
increase of it. 

The phenomenon of exhilaration can be studied better 
in the inhalation of chloroform, or nitrous oxide, than 
in the slower process of administering narcotics by the 
stomach. The exhilaration is the same, and in either 
case the power to feel impressions made on the sentient 
nerves is diminished from the beginning; and, if car- 
ried far enough, terminates in total insensibility, un- 
consciousness, and, finally, in death. 

375. Fascinating influence of Alcohol. — This ex- 
hilaration, always tending toward insensibility and 
unconsciousness, is that which renders alcohol so fas- 
cinating and so dangerous a poison. Its first effect is to 
render the victim unfit to judge of his own condition, 
of the nature and situation of things around him, or of 
his relations to these surroundings. Through the me- 
dium of the general nervous sensibility, we determine 
our condition of body and mind : through this medium 

we are conscious of our own powers, and determine. 
B. P.— 22. 



256 HYGIENE. 

with a good degree of accuracy, the physical, mental, 
and moral possibilities and duties of our situation. 
But the moment we place ourselves under the exhila- 
rating influence of alcohol, and in the exact ratio in 
which that influence affects us, we lose this power. 
Our judgment of ourselves, of our powers, and of our 
duties, is distorted and false, and this false judgment 
may lead us to ruin our health, corrupt our morals, 
and alienate our friends. 

376. The Action of Alcohol. — There are several 
fallacies connected with the too common indulgence in. 
alcoholic exhilaration, which demand exposure for the 
good of the young and the unguarded. There is an 
idea, widely entertained, that the effect of alcohol as 
seen in the furious, or the insensible state of drunken- 
ness, differs in hind from the exhilaration produced by 
a single glass of wine. This is not true. The action 
of alcohol on the nervous system is a unit: it is dimin- 
ished sensibility, manifesting itself in exhilaration, and 
this is drunkenness in kind, whatever the degree may 
be; and the exhilaration itself disqualifies the victim 
of it from judging of the degree. Hence, it follows 
that a man who has taken alcohol, and is under its 
influence, is drunk to that extent, but how much he is 
drunk he is not competent to know. 

377. The Danger of the Poison.— This last fact is 
a significant one, and solves the most profound 
social mystery of the past ages as well as of the pres- 
ent. It is this : Young men see the ruin of health, 
morals, fortune, character, and domestic happiness in 
the hundreds of their acquaintances, who go down to 
early and dishonored graves, victims of the drinking 



BRAIN TOISONS. 257 

habits of society, and yet they venture to travel the 
same dangerous road, when one of positive safety is 
open to their choice. 

They do not understand that the danger lies in tak- 
ing the poison, but suppose that it is in taking too 
much — an evil which they resolve always to avoid. 
But not understanding the nature of alcohol, nor 
knowing that to indulge in its exhilaration is, to that 
extent, to surrender the means of self-knowledge, and 
consequently of self-control, they move steadily on to 
ruin. A knowledge of the physiological effect of nar- 
cotics, and correct habits of life established on that 
basis, are the only safeguards against their fascina- 
tions. 

378. The Moderate Use of Alcohol.— The habitual 
use of alcoholic drinks, even though the quantity in- 
dulged in does not produce such drunkenness as will dis- 
qualify the subject for the ordinary business of life, w T ill 
yet leave the unmistakable traces of its effects in a dis- 
eased condition of the brain and nervous system. Sensi- 
bility in all the organs of the body will be more or less 
blunted; the pow T er to resist disease, and the ability to 
restore to healthy action the morbid condition of any 
organ or function, will be greatly impaired, the whole 
nutritive system will be found the subject of more or 
less derangement, and the force and endurance in the 
muscular system will feel the effect of the poison in a 
great diminution of its energy. Taken in this manner, 
it is a slow but very sure poison. 

Recapitulation. 

Narcotics render the food less subject to change, and, therefore, 
more difficult of digestion. Alcohol impairs sensibility in all the 



258 HYGIENE. 

organs. The exhilaration produced by alcohol is the result of 
diminished sensibility in the nervous system. This disqualifies 
the person to judge of his condition. Drunkenness differs in 
degree, but not in kind. The moderate use of alcohol is a dan- 
gerous delusion. 



LESSON XLVII. 



BRAIN POISONS — CONTINUED. 



379. Effects of Alcohol on the Mind —The effects 
of alcoholic drinks on the mental powers are among the 
most ruinous, as they are the most prominent of its 
morbid influences. Exhilaration is disturbed equilib- 
rium of nervous force, with a constantly progressing 
diminution of the aggregate of that force, ending in 
insensibility and delirium, and, finally, in unconscious- 
ness. 

While the powers of imagination are momentarily 
exalted, and the command of language is greater, the 
judgment is impaired, the power of perception is blunt- 
ed, and the reasoning faculties are rendered unreliable. 
With these derangements of the purely intellectual 
faculties, the passions are excited to morbid activity; 
and especially those of the grosser kind, being released 
from the restraint of the intellectual faculties and 
moral sensibilities, lead their victim into every species 
of debauchery and crime. 

380. Alcohol destroys Mental Harmony. — In the 

human constitution, the intellectual powers, the ani- 
mal appetites, the passions, and the moral affections 



UK. UN POISONS. 259 

are so adjusted that when a healthy balance of power 
is maintained among them, and a proper subordination 
observed, the result is the harmony of the whole group, 
bringing the highest happiness to the individual and 
the greatest good to society. 

The universal testimony of all ages, and every form 
of civilization, is, that the use of alcohol has every- 
where disturbed this nicely adjusted balance, and de- 
stroyed the equilibrium among these powers, bringing 
ruin on society, destruction on nations, and misery to 
its immediate victims, and to the domestic circle in 
which they moved. These disastrous results attract 
attention most where the poison is used in large quan- 
tities, but the effect is the same in kind, and is always 
in proportion to the quantity taken, other things being 
equal. 

381. Effects of Brain-poisoning. — The immediate 
effects of alcohol are temporary, and if the quantity 
taken be not very large, the disturbances pass off as 
soon as the alcohol can be discharged from the circula- 
tion by the lungs and other organs, and the nerves 
recover from its paralyzing influence. Fortunately, 
the poison is volatile, and its vapor passes through 
the membranes and other tissues of the body with 
scarcely any obstruction. From this cause, death 
seldom results immediately from alcoholic poisoning; 
but the secondary effects of the poison remain in a 
train of deranged physical functions and impaired or 
disturbed mental powers. 

The effect of alcohol on albumen is to coagulate it. 
Now, the brain consists largely of albumen, and alcohol 
acts on it as it does on the white of an egg, which is 



260 HYGIENE. 

nearly pure albumen : it hardens it, and thus destroys 
its delicate texture, and proportionally impairs all its 
functions. This effect has long been observed in the 
brains of habitual drunkards. 

382. Alcohol invites Disease. — The membrane which 
forms the walls of the air-cells in the lungs, as well as 
that which makes the fine capillary tubes of the pul- 
monary circulation, is highly albuminous in its char- 
acter. The effect of alcohol is to thicken these mem- 
branes, and thus interrupt the easy transmission of 
oxygen to the blood and of carbonic acid from it. This 
effect on the respiratory organs will usually relieve 
itself in a few days, but in the meantime the vitaL 
force is diminished with the reduced supply of oxygen, 
and the power to resist disease is greatly impaired. 

From this cause, those who use alcoholic drinks are 
more liable to be attacked with epidemic diseases than 
those who abstain. If the use of the poison becomes 
habitual, this effect, both on the brain and respiratory 
organs, will be rendered permanent, and impaired 
health and obtuse intellect will be entailed on the 
victim. 

383. Moral Effects of Brain-poisoning.— The im- 
pressions left on the mental and moral powers by long 
and frequent indulgence in the use of alcohol may be 
resolved into two classes: first, those arising from an 
enfeebled will-power; and, second, those springing from 
obtuse moral perceptions. Among the first results of 
even moderate drinking habits, w T e notice the loss of 
self-control. If the friends of the victim expostulate 
with him, and bring to his blunted and obtuse sen- 
sibilities a perception of his danger, he betrays a 



BRAIN POISONS. 261 

vacillating will — an inability to take a firm stand 
and guide his future course in the path of absolute 
Bobriety. 

. This inability of self-control gives rise to irregular 
and fitful moods of life, and betrays a want of confi- 
dence on the part of the victim, in his ability to carry 
out any good resolve which he may make. This weak- 
ening of the will-power betrays itself in the persistent 
drinking habits of those who are fully convinced of the 
ruin on which they are surely drifting, as well as in 
the numerous failures resulting from attempts at ref- 
ormation. 

384. Diminished Will-power. — The force of this 
drinking habit, of which so much has been said, re- 
solves itself chiefly into this feeble will-power. If we 
diminish the ability to resist a force, we do, practi- 
cally, the same thing as if we had increased that force. 
There is little doubt but this is merely a symptom 
indicating the diseased condition of the brain, present 
in the victim of the poison. 

While the unfortunate man of drinking habits may 
not be able to carry into action any good resolve, or 
guide his life to any virtuous end on account of an 
actually diseased condition of the brain, yet he is mor- 
ally responsible : his very disease is a crime — the crime 
of his youth. All either know or should know that 
alcohol is a poison, producing these effects, and to use 
it is to incur the consequences. 

385. Blunted Moral Sensibility.— Perhaps the effect 
of alcohol which is most to be deplored, is that which 
is exerted on the moral sensibilities. More than 
half the crimes that are committed in this country, are 



262 HYGIENE. 

either perpetrated under the immediate influence of 
alcoholic delirium, or may be traced directly to the 
blunting and paralyzing influence of the criminal's 
drinking habits. 

The nice perceptions of right and wrong, and the 
conscientious regard for the obligations of duty, are so 
impaired that the person who habitually takes the 
poison can stoop to low and dishonorable acts, or even 
to the commission of crimes, at which his moral sensi- 
bilities would have revolted when free from the degrad- 
ing influence of the poison. The social vices, such as 
gambling, licentiousness, etc., if not the direct out- 
growth of the drinking habits of society, are, at least, 
fostered by, and associated with these habits. 

386. How far these Derangements may be Cured. — 

After these injuries are inflicted on the brain and its 
appendages, the prospect of a permanent cure is very 
remote. If the patient be placed beyond the reach of 
the poison, as in an inebriate asylum, or be sustained 
by the encouraging council and sympathy of friends, 
and especially if he be kept constantly employed, he 
may, to some extent, restore a healthy action to the 
brain and reclaim its lost powers, but he is never safe. 
His impaired will-power is never restored to its origi- 
nal integrity. His only safety is in keeping beyond 
the reach of the poison. 

All experience proves that it is not safe for him to 
taste alcohol, even as a medicine. Here, as in other 
diseased conditions, the true policy is to prevent rather 
than cure, and, fortunately in this case, certain preven- 
tion is within easy reach of every one. It is simply not 
to drink alcohol in any form. 



TOBACCO. 263 

Recapitulation. 

Alcohol deranges the whole mental machinery, and destroys 
harmony of action between the mental and moral powers. Its 
immediate effects are temporary ; but, if the habitual use of alco- 
hol be established, the derangement will become permanent. 
The loss of self-control is among the first effects of drinking 
habits. Moral sensibilities are impaired by the use of alcohol. 
How far this diseased condition is curable. 



LESSON XLVIII. 

TOBACCO. 

387. Tobacco— its mode of Poisoning.— Tobacco is 
among the most powerful of the narcotic poisons which 
the vegetable kingdom affords. It differs from alcohol, 
however, in many particulars, which modify its effects 
on those who use it. As alcohol is the active poison in 
all the various forms of intoxicating drinks, so nicotine 
is the exhilarating agent in tobacco, whether it be 
chewed, smoked, or taken as snuff. This nicotine is an 
alkaline principle, volatile at a high heat; but, at 
ordinary temperatures, it is not converted into vapor 
in any sensible quantities, and, therefore, does not 
penetrate the membranes and pervade the tissues of 
the whole body as alcohol does ; and on this account its 
narcotic effects are slowly developed. 

In addition to its exhilarating effect, nicotine is di- 
rectly emetic, even when the poison is not taken into 
the stomach, but absorbed by the skin. While the 
paralyzing effects of alcohol begin with the nerves of 
B. P.— 23. 



264 HYGIENE. 

sensation, the action of tobacco is primarily on the nerves 
of motion, diminishing the contractile force of the 
muscles. 

388. Effect of Tobacco on Digestion, — From these 
characteristics, we will be prepared to learn that to- 
bacco produces its disturbances among the nervous and 
vital functions slowly, and often without the cause of 
these disturbances being suspected. 

We have already alluded (§ 269) to the effect of the 
use of tobacco on the saliva, and its influence on the 
perfect digestion of food, and we have only to add in 
this place, that, in common with all narcotics, tobacco 
has a tendency to prevent change in the composition 
of organic substances, although this tendency is feeble 
compared with that of alcohol. 

The proportion of the food digested in the stomach 
of those who use tobacco, compared with the digestive 
action of those who do not use it, nor any other nar- 
cotic, is greatly in favor of the latter class, other things 
being equal. 

389. Tobacco diminishes the Desire for Food.— 

The specific effect of tobacco on the stomach, tending 
more or less toward nausea, has the effect to diminish 
the desire for food; and though the rate at which the 
tissues are transformed is perceptibly diminished, yet 
leanness, and sometimes emaciation, result from the 
use of tobacco. Perhaps it was this peculiar effect of 
tobacco which first prompted its use among savages 
(who w r ere subject to great irregularity in the supply 
of food), that they might endure starvation without 
suffering the pain of hunger. 

The ultimate effect of tobacco, however, is to slowly 



TOBACCO. 265 

reduce the aggregate of the vital force, impairing first 
the motor functions of the nervous system, affecting the 
involuntary motions more directly than the voluntary. 
The senses most seriously affected by the use of this 
poison are taste and smell, but this is probably owing 
to the local action in the method of using it. 

390. Strength of the Tobacco Habit —The feeling 
of exhilaration from the use of tobacco is hardly percep- 
tible until its action is withdrawn, when a sense of 
irritability and indescribable wretchedness takes pos- 
session of the victim of the poison, and will not yield 
to any terms till the exhilaration is restored. Where 
the habit is of long standing, and the quantity used is 
large, the feeling of irritability on being deprived of it 
sometimes amounts to actual insanity for the time 
being. 

The habit, from this cause, is even more inveterate 
than that of using alcoholic drinks, and the power of 
voluntary control over the habit appears to be as com- 
pletely paralyzed by tobacco as by the more powerful 
narcotics. No one is sensible of the effects of tobacco 
on the nervous system till he has abandoned the use of 
it, and so far recovered from its effects as to have lost 
the desire for its peculiar exhilaration. 

391. Effect of Tobacco on the Mental Functions. — 

Tobacco exerts its characteristic influence on the in- 
tellectual functions. Its action is slow, and its ex- 
hilaration at any time almost imperceptible; but in a 
series of years it works most disastrous consequences, 
impairing first the power of decision — the will-power; 
after that, the memory feels its effects, the finer moral 
feelings are blunted, and the mental perceptions — the 



266 HYGIENE. 

powers of abstract thought — are impaired, and the 
whole mental fabric, slowly undermined, falls into 
ruin. 

So stealthy is its approach, so insidious its march, 
that neither the victim nor his friends suspect the 
cause of his feeble health and failing mind; and 
even when the faithful physician has the sagacity to 
detect the cause, and professional honor enough to tell 
the whole truth without concealment, the chances are 
greatly against the patient's being able to exercise self- 
control enough to apply the proper remedy — the entire 
disuse of the poison in every form. 

392. Duration of human Life affected by Tobacco.— 

Though tobacco is so active, and so virulent a poison, 
yet it is rarely the immediate and direct cause of 
death; and it has even been affirmed by good physi- 
ologists that its use has not diminished the average 
duration of human life. This does not follow, however, 
from the fact by which it is sought to be established. 

If the duration of human life now is as great as it 
was two hundred years ago, or before tobacco came into 
general use, it must be remembered that the average 
comfort and protection of man has greatly increased, 
and his knowledge of the laws of health and his means 
of controlling diseases, have been greatly advanced in 
that period; and if human life has not been corre- 
spondingly prolonged, there must be some counteract- 
ing cause. May not that cause be found in the use of 
alcohol and tobacco? 

393. Early Decay, one of the Effects of Tobacco.— 

Whatever may be the influence of tobacco on the 
health and vital force of those who lead lives of mus- 



TOBACCO. 267 

cular activity in the open air, there can be no question 
of its pernicious effects on persons of sedentary habits, 
and especially on those devoted to mental pursuits. 

The victim of the tobacco poison makes an apology 
for the use of his cigar by declaring that it gives force 
and clearness to his mental operation, and yet he does 
not perceive that even that apology is an admission of 
the fearful effects of the poison on brain action. If a 
man has so reduced his brain-power that it is necessary 
to cut off the vital force from the nervous extremities, 
in order to supply the force for efficient brain action, 
he is certainly on the road to mental imbecility and 
physical decrepitude. There is no doubt but that thou- 
sands destroy years of their ripest usefulness, and in- 
duce imbecility and second childhood, by the habit of 
using tobacco. 

394. Opium — its peculiarities as a Poison. — Opium 
has long been used in China and Japan as alcohol and 
tobacco are used in Europe and America. Within the 
last half century, the use of opium as an exhilarant has 
been increasing with alarming rapidity in this country. 

It is a narcotic, less diffusible than alcohol, but more 
active than tobacco, in the ordinary modes of its use. 
It is equally as fascinating in its influence as either of 
those poisons; and the fact that it may be used for 
years and yet its use kept a secret, gives it a power 
that neither of those can exert. Tobacco and alcohol 
betray their victims, but opium keeps the secret for 
them till it binds them so securely in its fetters that 
escape is almost impossible. Safety is found only in 
firmly discarding the use of all narcotics, except when 
absolutely demanded in acute disease. 



268 HYGIENE. 

Recapitulation. 

Tobacco is a less volatile poison than alcohol. Its effect on the 
saliva impairs digestion, and the tendency to induce nausea dim- 
inishes the desire for food. The exhilaration from tobacco is 
feebler than that from alcohol; but, when the habit is formed, 
the desire for it is equally strong. Tobacco slowly, but very cer- 
tainly, impairs all the mental functions of the brain, and produces 
early decay and premature old age. Opium, as an exhilarant, 
stands intermediate between alcohol and tobacco. Its use is 
more easily concealed than is the use of alcohol or tobacco. 



LESSON XLIX. 

BRAIN EXERCISE AND REST. 

395. Early failure of Mental Faculties.— The brain, 
as the instrument of thought, acquires power and tact 
by exercise and judicious use. This aptitude is much 
more readily acquired when the brain action is regu- 
lar and habitual. Persons who have accustomed them- 
selves to exercise the mind in thought under certain 
circumstances, or in connection with certain movements 
of the body, will find it very difficult to bring all their 
mental powers to bear under different circumstances. 

The duration of mental activity, or the period of life 
when mental force begins to fail, is a subject which is 
attracting much attention, both on account of its in- 
trinsic importance, and because that in different per- 
sons this decrepitude of old age appears at periods so 
widely different. Much of this may depend on hered- 
itary constitutional peculiarities, but more will be found 
to be connected with the modes of mental training. 



BRAIN EXEBCISE AND REST. 2G9 

Minds not trained to think soon fall into decay; and 
those in which the training has heen confined to a few 
faculties, and in which all the others have been neg- „ 
lected, fail early in life. A broad and general training 
of all the faculties, and the uniform exercise of them, 
will secure the greatest exemption from the mental 
infirmities of age, other things being equal. 

396. Brain rest — its necessity in brain labor. — 

But brain activity demands rest, as activity every- 
where in the vital machinery calls for its period of 
repose. The powers of thought may be relieved some- 
what by changing the mode of thought, and trans- 
ferring the mental activity to other channels; but 
actual brain rest is obtained only in sound sleep. 

The notion which was so popular a few years ago, 
that students and brain-workers in general require 
but little sleep, is not only false but most pernicious 
in its consequences to the student who reduces it to 
practice. The romance of the "midnight lamp" has 
been a very expensive luxury, dimming many of the 
brightest stars of human genius. 

397. Sleep should be in proportion to brain activ- 
ity. — Sleep should be periodical and habitual, if we 
would derive the greatest benefit from it as a restorer 
of wasted brain force. As activity naturally associates 
itself with light, so the repose of sleep is associated 
with darkness; and as the day of twenty-four hours is 
nearly equally divided (taking the whole year together) 
between light and darkness, there is a very suggestive 
hint as to the proper proportion of time to be devoted 
to rest. This will depend very much, however, on the 
intensity of brain action. 



270 HYGIENE. 

If the mind could be trained to endure twelve con- 
secutive hours of labor, the succeeding twelve hours 
should be devoted to sleep, in order to repair the waste 
of such a protracted effort. But such prolonged activity 
is possible in but few persons; and even where it is 
possible, it is bad economy. With the best trained 
and disciplined thinkers, about two hours of close appli- 
cation is the extent of time which can be economically 
employed without an interval of relaxation. 

398. Wakefulness— its effect and its remedy.— The 

student whose life is properly divided between activity 
and rest, will find that from eight to ten hours of quiet, 
sound sleep will be sufficient to maintain the highest 
mental vigor. Persons of irritable, nervous systems 
and of studious habits often fail to sleep soundly. This 
wakefulness may be generally overcome by establishing 
and rigidly maintaining the habit of retiring and 
rising at certain hours. 

A firm mattress, a well ventilated bedroom, a light 
and early supper, and a cold sponge bath before lying 
down, will seldom fail to procure sound sleep. The 
habit of sleeping at intervals during the day, and 
especially the regular after-dinner siesta, greatly inter- 
feres with the sound and refreshing quality of the 
night's repose. Sleep can never be refreshing while 
the stomach is engaged in the business of digestion, 
and for this reason we should never eat within two 
hours of our time of retiring. 

399. Light — its effect on brain activity. — Carefully 
conducted experiments have established the principle 
that sleep is more invigorating when the sleeper is in 
the dark than in sunlight; and, conversely, that activ- 



BRAIN EXERCISE AND REST. 271 

ity is best sustained in sunlight, either direct or dif- 
fused. These are truths too intimately connected with 
health to be neglected with impunity. Sunshine exerts 
a strange force on brain activity, augmenting the power 
with which the whole vital machinery operates. 

Persons who work in mines by means of artificial 
light, and those who live in badly lighted apartments, 
soon show the effects of this want of sunshine in the 
reduced color of the blood, the general relaxation of the 
muscular system, and the diminished mental activity. 

400. Best Time for Sleep. — In securing the number 
of hours of sleep which we propose, the time of retir- 
ing should be fixed so that sleep will not trespass on 
the sunlight of the morning. One hour in the morning 
is worth more for mental labor than two hours after ten 
o'clock in the evening. To retire early and rise at day- 
light is the order of nature, and they who violate it 
will, sooner or later, pay the penalty. Late and irreg- 
ular hours, inducing dreamy slumber rather than sound 
sleep, will dissipate brain force, and destroy both mental 
vigor and physical health. 

401. Reduction of Vital Force in Sleep. — Sound, 
refreshing sleep is a state of absolute inaction of all 
the voluntary functions, and of entire unconsciousness 
with regard to ourselves or our surroundings. The in- 
voluntary functions sympathize with this state of rest, 
and the force expended in their performance is mate- 
rially reduced. The circulation becomes slower, the 
pulse softer and less forcible, and the breathing is 
neither so full nor so frequent. 

This reduction of vital action during sleep brings 
several important suggestions. In sleep we are more 



272 HYGIENE. 

susceptible to the action of external agencies which 
tend to produce disease than when awake, and there- 
fore we should be careful to guard against them. 

Sleeping apartments should be well supplied with 
fresh air, but its introduction should be so arranged 
that the sleeper will not be in the direct current, or 
draft. The production of animal heat is reduced during 
repose, and on this account the sleeper should be pro- 
tected by sufficient covering to secure comfort. 

402. Procuring Sleep by Medicine. — Among the 
many errors with regard to sleep, none is more mis- 
chievous than the habit of resorting to medicine to 
relieve sleeplessness. Anodynes and narcotics never 
produce natural, refreshing rest; and the disturbance 
in the nervous system, left as the result of the remedy, 
is generally more injurious than the wakefulness it was 
intended to relieve. 

The most dangerous effect to be dreaded in such use 
of medicine, is the necessity of repeating and even 
increasing the dose till the habit becomes too strong 
to be broken. But it is especially in behalf of infants 
that we enter our solemn protest against the whole 
family of anodynes, cordials, soothing syrups, etc. No 
human power of computation can measure the mischief 
done to helpless humanity in this way while yet in the 
cradle. 

Recapitulation. 

The duration of the period of mental activity is dependent on a 
variety of causes. Uncultivated minds fail at an earlier period 
than those properly trained. Sleep necessary to maintain mental 
vigor. It should be periodical, and reduced to a habit. Wakeful- 



BRAIN EXERCISE AND REST. 273 

ness — its remedy. Sleep should be in the night, and should be 
a state of absolute unconsciousness. Rest should not be pro- 
cured by anodyne medicines. 



LESSON L. 



ACCIDENTS AND DISEASES. 



4:03. Injuries from Accident. — It has been the 
object of these lessons to communicate such a knowl- 
edge of the laws of life as will put the student in pos- 
session of the means of preserving health and vigor 
under all ordinary circumstances. But with our present 
surroundings we are liable to injuries from accidents 
and casualties, which no prudence or foresight can 
avoid; and even diseases may attack us, that no in- 
herent vigor of health or vital force will be sufficient 
to throw off. 

If, as has been said, "good health is not only a 
blessing, but a duty," it must be admitted to be, some- 
times, a duty very difficult of performance. It is im- 
portant, therefore, that every body should understand 
something of the management of the minor accidents 
to which mankind is subject, and how to treat the 
slighter disturbances of health so as to prevent them 
from passing into the more formidable types of disease. 

404. Bleeding from Wounds. — In a majority of 
cases of minor accidents or of threatened disease, it is 
not so difficult to know what should be done as what 
should not be done. One of the great difficulties in 
these cases is to manage the ignorant officiousness of 



274 HYGIENE. 

kind and benevolent persons, who often do immeas- 
urable mischief when prompted by the very best of 
motives. 

In all cuts or wounds made by sharp instruments, 
the first thing that demands attention is the bleeding. 
If the blood flows rapidly and in jets, we will under- 
stand that an artery is injured, and our business is to 
make pressure on the bleeding vessel near the wound, 
on the side toward the heart, by the best means that 
we can devise. Having thus temporarily arrested the 
bleeding, a surgeon should be obtained immediately, 
and the artery secured by a ligature. If the injured 
vessel be on the scalp, it may be permanently closed by 
continued pressure. 

405. Treatment of Cuts by sharp instruments. — If, 

however, the bleeding be in a regular, constant stream, 
we may be assured that the blood is flowing from a 
vein or veins. In this case nothing more is necessary 
than to apply cold water freely until the bleeding has 
abated, when the edges of the wound should be care- 
fully drawn together and secured, in actual contact 
with each other, by strips of adhesive plaster: and 
where the parts admit of it, the dressings should be 
supported by a light bandage, applied with only a 
moderate degree of tightness. This dressing should not 
be removed for five or six days, but may be frequently 
wet with cold water. All that is necessary is that the 
divided edges be maintained in contact, with nothing 
between them, and that the air be carefully excluded 
from the injured part. 

That is a mischievous error which supposes that 
salves, ointments, and stimulating applications have 



ACCIDENTS AND DISEASES. 275 

healing virtues. Injuries of this kind can be repaired 
only by the vital force producing new cells, and with 
these uniting the divided tissues and thus repairing 
the injury. 

406. Bruises and Burns — how treated. — In bruises 
and lacerated wounds, the exclusion of the air and the 
application of cold water, to keep down excessive in- 
flammation, together with absolute freedom from mo- 
tion in the parts, comprise all that is necessary to be 
done. After suppuration has commenced, the wound 
should be frequently washed with tepid water, and the 
parts supported by an appropriate bandage. 

In burns and scalds where the cuticle has been 
removed, and a large surface of the true skin exposed, 
the important matter is to secure protection from the 
air. This may be done by saturating cotton batting or 
some other soft substance with glycerine, or oil of any 
kind that is not rancid or stimulating. The object 
is to substitute for the cuticle something that will pro- 
tect the sentient extremities of the nerves from ex- 
posure, which is the cause of the excruciating pain of 
burns. 

407. The approach of Acute Diseases. — Fevers, and 
most acute diseases, are preceded by a sense of languor, 
an indisposition to activity, and a loss of appetite. 
Admonished by these symptoms, the body should be 
sponged with tepid water so as to thoroughly relieve 
any mechanical obstruction of the perspiratory pores. 
This should be followed by brisk friction with a flesh- 
brush or rough crash towel till a glow of heat is felt 
over the surface of the skin. 

Follow this with absolute quiet, both of body and 



276 HYGIENE. 

mind, and limit the food to gruel, beef tea, or thin por- 
ridge, taking even these only as the appetite calls for 
them. If twenty-four hours of this treatment brings no 
relief, your physician should be consulted. Avoid all 
excitants, stimulants, or exhilarants, and resist all per- 
suasions to take solid food when the appetite admon- 
ishes you of the inability of the stomach to digest it. 

408. Diarrhea and Habitual Costiyeness.— In warm 

weather, it frequently occurs that the perspiration 
is suddenly checked, and the fluids thrown to the 
internal surface produce a troublesome diarrhea. All 
that is necessary in this condition, in ordinary cases, is 
to use the tepid bath and flesh-brush, drink copiously 
of slippery-elm water, or flaxseed tea, and abstain from 
solid food and from all nostrums which promise to cure 
bowel complaints. 

Some persons are much troubled with habitual con- 
stipation of the bowels. Diet and exercise are the 
remedies for this troublesome condition. Bread made 
of unbolted flour, with a free use of succulent vege- 
tables and ripe fruits, will seldom fail to relieve the 
most stubborn case of costiveness, if the patient takes 
sufficient exercise in the open air. 

409. Selection of a Physician. — But few duties de- 
volve on the heads of families more important, and, to 
most persons, more difficult, than the selection of a 
family physician. This difficulty is greatly increased 
by the fact that people in general, though well edu- 
cated, and intelligent on other subjects, know but little 
of the physiological laws underlying the whole subject 
of health. 

A physician should, first of all, be possessed of a large 



ACCIDENTS AND DISEASES. 277 

endowment of common sense and moral honesty. To 
these indispensable qualities should be added a thor- 
ough knowledge of medical science in all its depart- 
ments, and a well-trained faculty of close observation 
and patient investigation of the phenomena of health 
and disease, as they will be presented to him in his 
daily routine of business. 

Firmness and decision are traits of character which 
will be largely in demand in his daily intercourse with 
the sick. The impudence of quackery, the ignorant 
officiousness of well-meaning friends, and the vacilla- 
ting indecision of the sick, demand that, for the safety 
of the patient and the maintenance of his own good 
name and clear conscience, the physician should exer- 
cise an unfaltering firmness. 

410. Medicines — their use and abuse. — Among the 
most pernicious ideas wdiich have possessed the public 
mind, is the notion that health may be disregarded, 
since we have medicines to cure all the diseases our 
recklessness may induce. Let the public learn that 
medicine is always an evil — a great evil, though it may 
be necessary in order to obviate a greater evil. 

One of the most unaccountable traits in the character 
of modern society is the propensity to swallow drugs, 
and to be deluded by the boastful pretensions of igno- 
rant venders of nostrums, warranted to cure all dis- 
eases, restore shattered constitutions, and be a perfect 
substitute for a careful observance of the laws of health. 
The faithful physician has no higher duty to perform, 
than to properly inform the public mind on this sub- 
ject and correct these fearful abuses. But this demands 
a large share of moral honesty and self-denial, for the 



278 HYGIENE. 

ill health of the country, which gives him his business, 
is largely the result of this ignorant and indiscriminate 
use of medicines. 

411. Preservation of Health a Moral Duty.— There 
is a moral obligation resting on every one to preserve 
and maintain the highest health that is attainable, 
both of body and mind. God has created us for the 
discharge of important duties in life, and the fulfill- 
ment of this Divine purpose depends on the health 
that will give us ability equal to the task, Within 
certain limits, the means of health are placed in our 
own hands, and we can not, ignorantly or recklessly, 
disregard its conditions without incurring guilt. 

We have no more right to render our life a failure 
than we have to commit suicide. Moreover, the laws 
of life and health are Divine laws, emanating from the 
wisdom and benevolence of the Creator, and to violate 
them is rebellion against his authority. Our own hap- 
piness, the greatest good of society, and our regard for 
the Divine authority, all conspire to demand of us a 
thorough knowledge and faithful observance of the 
Law t s of Health. 

Recapitulation. 

Accidental injuries are unavoidable, therefore every person 
should have some knowledge of their treatment. Bleeding from 
an artery can be arrested only by a ligature. Cuts from sharp 
instruments require simple dressings. In burns and scalds the 
surface must be protected. The selection of a physician is a 
difficult and responsible task. Medicines, though sometimes 
necessary, are always to be regarded as evils. 



Index. 



B. P.— 24. 



INDEX. 



Absorbents, 39. 
Abstinence from food, 199. 
Abstract thought, a human pecu- 
liarity, 16. 
Adjustment of the eye, 121. 
Air, composition of, 43. 

means of purifying it, 212. 
sources of its impurity, 212. 
Air-cells in the lungs, 42. 
Alcohol, its effect on respiration, 
250. 
its chemical relations, 248. 
effect on the transformation 

of tissues, 250. 
diminishes muscular force, 

251. 
its influence on animal heat, 

252. 
its influence on mind, 258. 
how far its effects are curable, 
262. 
Amylaceous food, 163. 
Anastomosing vessels, 39. 
Anatomy defined, 13. 
Animals, how distinguished from 
vegetables, 9. 



Animal sub-kingdoms, 10. 

Animal functions, 14. 

Animal food, 168. 

Aorta, 34. 

Appetite, when safe to follow, 184. 

bribing the, 189. 
Aqueous humor of the eye, 116, 119. 
Arachnoid membrane, 87. 
Arm, the bones of, 68. 
Arteries, their office, 34. 

how distributed, 35. 
Articulate animals, 11. 

language, 79, 82. 
Articulations, 61. 
Arytenoid, cartilage, 80. 
Atmosphere, composition of, 211. 
Auricles, 32. 

B 

Bathing, 222. 

Baths, plunge and shower, 224. 
Beans as food, their character, 172. 
Beef, its food value, 168. 
Birds, 12. 

Bleeding from an artery, how dis- 
tinguished, 37. 

how arrested, 274. 

(281) 



282 



INDEX. 



Bloody the means of purifying it, 48. 

its composition, 53. 

quantity of, 57. 
Blood disks, 54. 
Bones, their use, 58. 

their composition, 59. 

mechanism of, 60, 74. 

not sensitive, 61. 

their hygiene, 228. 

liability to distortion, 228. 
Brain, anatomy of, 85. 

gray and white matter in, 87. 

complex function of, 90. 

its connection with mental 
functions, 138. 

rest in sleep, 145. 

exercise of, 243. 
Bread, its importance as food, 178. 

rules for making, 178. 
Breathing, how performed, 45. 

purpose of, 46. 

too frequent, effect of, 208. 

imperfect, effect on health, 
209. 

its direct connection with 
life, 210. 
Bronchia, 42. 
Burns, how treated, 275. 
Butter, its food value, 166. 

C 

Caecum, 28. 

Capillaries, 35. 

Cardiac orifice, 24. 

Carpus, the hones of, 69, 70. 

Cartilage, cricoid, 79. 



Cartilage, arytenoid, 80. 

thyroid, 79. 
Cells compose the tissues, 55. 

how formed, 55. 

transformation of, 57. 
Cerebro-spinal axis, 85. 
Cerebrum and cerebellum, 86. 
Cerebrum, connected w T ith thought, 

139. 
Cheese as food, 166. 
Chemical changes, 47. 
Chyle, 30. 
Chyme, 26. 

Circulation of the blood, 31-40. 
Classification of bodies, 7. 
Clavicle, 69. 
Clothing, its relation to health, 224. 

material of, 225, 226. 
Coccyx, 68. 
Cochlea, 105. 

Coffee as a diet drink, 158. 
Colon, 28. 

Coma, how it differs from sleep, 114. 
Comparative anatomy defined, 13. 
Compression of the chest, 207. 
Cooking food, 175. 
Cranial arch, 65. 

nerves, 88. 
Cranium, bones of, 64. 
Cricoid cartilage, 79. 
Crystalline lens, 116, 119. 

D 

Diaphragm, 43, 44. 
Digestion, how performed, 25. 
Disease defined, 151. 



INDEX. 



283 



Draft of air, exposure to, 221. 
Duodenum, 27. 

Dura Mater, 86. 

E 

Ear, external, 101. 

drum of, 102. 
Ear, bones of, 103. 
Eating between meals, 192. 
Economy of motion, 75. 
Eggs as food, 167. 
Epiglottis, 80. 
Ethmoid bone, 65. 
Eustachian tube, 102. 
Evaporation, a cooling process, 217. 
Exercise varies the quantity of 
food, 188. 

rules for, 237. 
Exhilaration explained, 255. 
Eye, the anatomy of, 111-117. 

F 

Face, bones of the, 65. 

Femur, 70. 

Fermented drinks, 158. 

Fermenting bread, 178. 

Fibula, 70. 

Fishes, 12. 

Flour, varieties of, 170. 

adulterations of, 170. 
Food classified, 19, 160-164. 

and drink, 154-159. 

quality of, 165-174. 

preparation of, 175-179. 

auxiliary, 180-184. 

quantity, time of, 185-195. 



Frontal bone, 64. 

G 

Ganglions, 84, 129. 
Glands, 48. 

salivary, 21. 

lymphatic, 38. 

oil, 50. 

lachrymal, 113. 
Glottis, 80. 

Growth and repair, 52. 
Gymnastic exercise, 238. 

H 

Hand, bones of, 69. 
Head, bones of the, 64. 
Hearing, 106-111. 

mechanism of, 108. 
Heart, its anatomy and action. 

32-34. 
Heat, its source in animals, 47. 

means of reducing, 220. 
Heat-producing food, 163. 
Hemispheres of the brain, 85. 
Humerus, 69. 
Hygiene defined, 149. 



Ileo-colic valve, 28. 

Ileum, 27. 

Images on the retina, how formed, 

120. 
Injuries from accidents, etc., 273. 
Innominatum, 68. 
Inorganic bodies, 8. 
Intercostal muscles, 44. 
Intestinal canal, its anatomy, 26, 29. 



284 



INDEX. 



Involuntary motions, 128. 
Iris, 115. 



Jejunum, 27. 

Joints, anatomy of, 61, 62. 

Jugular Vein, 202. 

K 

Kidneys, their office, 49. 
Knee-pan, 70. 



Labyrinth of the ear, 104. 

Lachrymal gland, 113. 

Lacteals, their function, 27. 

Larynx, 79, 82. 

Life-force, 56. 

Life, graduated scale of, 141. 

Ligaments, 61. 

Light and brain activity, 270. 

Liver, its function, 29, 48. 

Lungs, 41, 42. 

Lymphatic vessels, 38. 

M 

Mammalia, class of, 12. 
Man, compared with the lower 
animals, 15. 

his mental superiority, 142. 
Manual labor as exercise, 239. 
Mastication, 19. 

importance of, 193. 
Meat, how to select it, 169. 

modes of cooking, 175. 



Medulla Oblongata, 86. 

Mesentery, 27. 

Metatarsus, 71. 

Milk as a diet, 165, 166. 

Mind, its effect on the circulation, 

204. 
Moderate drinking, 257. 
Modulation of voice, 82. 
Mollusks, 11. 

Motor and sentient nerves, 91. 
Mouth, 19. 
Muscles, their anatomy, 72. 

their arrangement, 74. 

number of, 77. 
Muscular contraction, its effect on 
the circulation, 202. 

exercise, its effect, 232. 
Musical faculties, 109. 

N 

Nerves, 88-95. 

distribution of, 92. 

of special sense, 91. 
Nervous system, 83. 

peculiar to animals, 10. 
Nervous terminations, 92. 
Nutrition of animals and plants, 14. 

O 

Occipital bone, 65. 

(Esophagus, 23. 

Oil glands, 49. 

Oils and fats as food, 164, 180. 

Olfactory nerve, 89, 91. 

Opium, a brain poison, 267. 



INDEX. 



285 



Optic nerve, SO, 01. 
Organic bodies, 7. 

character of, 8. 
, Organs of special senses, 101. 
Ossification, 59. 
Over-heated rooms, 219. 
Oxygen, its office in respiration, 
213. 



Pacinian corpuscles, 93. 
Pancreas, 29. 
Parietal bones, 64. 
Parotid glands, 21. 
Patella, 70. 
Pelvis, bones of, 68. 
Peritoneum, 25. 
Perspiratory glands, 49. 
Pharynx, 22. 
Physiology defined, 13. 

its relation to hygiene, 150. 
Pia Mater, 86. 
Plexus, Brachial, 90. 

Lumbar, 90. 
Potato, its food value, 173. 
Proteine food, 161. 
Protozoans, 10. 
Pulse, 36. 

Pupil of the eye, 115. 
Pyloric orifice, 25. 

Q 

Quadrumana, 15. 
Quality of food, 165. 
Quantity of food, 185. 



R 

Radiate animals, 11. 

Radius, 69. 

Reflex motions, 134. 

Relation of mind to matter, 247, 

Reptiles, 12. 

Respiration, organs of, 41. 

its mechanism, 44. 

its use, 46. 
Rest, its importance, 241. 
Retina, 115. 
Ribs, action of the, 44. 

anatomy of, 67. 

their movements in breath- 
ing, 206. 



Saliva, its use, 22. 
Salivary glands, 21. 
Salt necessary to health, 181. 
Scapula, 69. 
Sebaceous follicles, 49. 
Secretion, 21. 
Semicircular canals, 104. 
Sensation, method of, 94. 

grades of, 97. 
Sentient nerves, 91. 
Sesamoid bones, 71. 
Short-sightedness, 123. 
Skeleton, 58, 63. 
Skin, its anatomy, 49. 
Skull, 64. 
Sleep, 143. 

true brain rest, 269. 

proper time for, 271. 



286 



INDEX. 



Smelling, sense of, 98. 

Soda, its use in cooking, 183. 

Sound, nature of, 106. 

transmission of, 107. 

Sphenoid bone, 65. 

Spinal column, 65, 66. 
nerves, 89. 

cord, special functions of, 
133. 

Spine, curvature of, 231. 

Spleen, 31. 

Sternum, 68. 

Stomach, its anatomy and func- 
tion, 29. 

Sublingual glands, 22. 

Submaxillary glands, 22. 

Sunlight, its influence on health, 
235. 

Sympathy of the heart with other 
organs, 201. 

Symphysis, 63. 



Tarsus, bones of, 71. 
Tea as a diet drink, 158. 
Tears, 113. 
Teeth, classification of, 20. 

rules for preserving, 194. 
Temperature of the body in health, 
51. 

effect of on the circulation, 
203. 
Temporal bones, 64. 
Tendons, their form and use, 73. 



Thoracic duct, 30. 

Thorax, 41. 

Thought, a human attribute, 16. 

how related to brain, 138. 
Thyroid cartilage, 79. 
Tibia, 70. 
Tissues, 17. 
Tobacco, its effect on saliva, 26. 

its mode of action on brain 
functions, 263. 

its effect on digestion, 264. 
Trachea, 42. 
Tricuspid valves, 33. 
Turbinated bones, 99. 

U 

Ulna, position of, 69, 70. 



Valves of the heart, 33, 34. 
Veins, 34, 36. 

valves of the, 37. 

effect of pressure on, 201. 
Vena Cava, 35. 
Ventricles, 32. 
Vertebrse, anatomy of, 66. 
Vertebrate animals, 12. 
Vision, 117-127. 
Vocal cords, 80. 
Voice, pitch of, 81. 

W 

Warming apartments, 214. 
Water, sources of impurity of, 156. 



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